linux-toradex.git/kernel/locking, branch v6.16-rc6 Linux kernel for Apalis and Colibri modules Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2025-06-02T19:24:58+00:00 Linus Torvalds torvalds@linux-foundation.org 2025-06-02T19:24:58+00:00 7f9039c524a351c684149ecf1b3c5145a0dff2fe Pull more kvm updates from Paolo Bonzini: Generic: - Clean up locking of all vCPUs for a VM by using the *_nest_lock() family of functions, and move duplicated code to virt/kvm/. kernel/ patches acked by Peter Zijlstra - Add MGLRU support to the access tracking perf test ARM fixes: - Make the irqbypass hooks resilient to changes in the GSI<->MSI routing, avoiding behind stale vLPI mappings being left behind. The fix is to resolve the VGIC IRQ using the host IRQ (which is stable) and nuking the vLPI mapping upon a routing change - Close another VGIC race where vCPU creation races with VGIC creation, leading to in-flight vCPUs entering the kernel w/o private IRQs allocated - Fix a build issue triggered by the recently added workaround for Ampere's AC04_CPU_23 erratum - Correctly sign-extend the VA when emulating a TLBI instruction potentially targeting a VNCR mapping - Avoid dereferencing a NULL pointer in the VGIC debug code, which can happen if the device doesn't have any mapping yet s390: - Fix interaction between some filesystems and Secure Execution - Some cleanups and refactorings, preparing for an upcoming big series x86: - Wait for target vCPU to ack KVM_REQ_UPDATE_PROTECTED_GUEST_STATE to fix a race between AP destroy and VMRUN - Decrypt and dump the VMSA in dump_vmcb() if debugging enabled for the VM - Refine and harden handling of spurious faults - Add support for ALLOWED_SEV_FEATURES - Add #VMGEXIT to the set of handlers special cased for CONFIG_RETPOLINE=y - Treat DEBUGCTL[5:2] as reserved to pave the way for virtualizing features that utilize those bits - Don't account temporary allocations in sev_send_update_data() - Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM, via Bus Lock Threshold - Unify virtualization of IBRS on nested VM-Exit, and cross-vCPU IBPB, between SVM and VMX - Advertise support to userspace for WRMSRNS and PREFETCHI - Rescan I/O APIC routes after handling EOI that needed to be intercepted due to the old/previous routing, but not the new/current routing - Add a module param to control and enumerate support for device posted interrupts - Fix a potential overflow with nested virt on Intel systems running 32-bit kernels - Flush shadow VMCSes on emergency reboot - Add support for SNP to the various SEV selftests - Add a selftest to verify fastops instructions via forced emulation - Refine and optimize KVM's software processing of the posted interrupt bitmap, and share the harvesting code between KVM and the kernel's Posted MSI handler" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (93 commits) rtmutex_api: provide correct extern functions KVM: arm64: vgic-debug: Avoid dereferencing NULL ITE pointer KVM: arm64: vgic-init: Plug vCPU vs. VGIC creation race KVM: arm64: Unmap vLPIs affected by changes to GSI routing information KVM: arm64: Resolve vLPI by host IRQ in vgic_v4_unset_forwarding() KVM: arm64: Protect vLPI translation with vgic_irq::irq_lock KVM: arm64: Use lock guard in vgic_v4_set_forwarding() KVM: arm64: Mask out non-VA bits from TLBI VA* on VNCR invalidation arm64: sysreg: Drag linux/kconfig.h to work around vdso build issue KVM: s390: Simplify and move pv code KVM: s390: Refactor and split some gmap helpers KVM: s390: Remove unneeded srcu lock s390: Remove unneeded includes s390/uv: Improve splitting of large folios that cannot be split while dirty s390/uv: Always return 0 from s390_wiggle_split_folio() if successful s390/uv: Don't return 0 from make_hva_secure() if the operation was not successful rust: add helper for mutex_trylock RISC-V: KVM: use kvm_trylock_all_vcpus when locking all vCPUs KVM: arm64: use kvm_trylock_all_vcpus when locking all vCPUs x86: KVM: SVM: use kvm_lock_all_vcpus instead of a custom implementation ... 
Pull more kvm updates from Paolo Bonzini:
  Generic:

   - Clean up locking of all vCPUs for a VM by using the *_nest_lock()
     family of functions, and move duplicated code to virt/kvm/. kernel/
     patches acked by Peter Zijlstra

   - Add MGLRU support to the access tracking perf test

  ARM fixes:

   - Make the irqbypass hooks resilient to changes in the GSI<->MSI
     routing, avoiding behind stale vLPI mappings being left behind. The
     fix is to resolve the VGIC IRQ using the host IRQ (which is stable)
     and nuking the vLPI mapping upon a routing change

   - Close another VGIC race where vCPU creation races with VGIC
     creation, leading to in-flight vCPUs entering the kernel w/o
     private IRQs allocated

   - Fix a build issue triggered by the recently added workaround for
     Ampere's AC04_CPU_23 erratum

   - Correctly sign-extend the VA when emulating a TLBI instruction
     potentially targeting a VNCR mapping

   - Avoid dereferencing a NULL pointer in the VGIC debug code, which
     can happen if the device doesn't have any mapping yet

  s390:

   - Fix interaction between some filesystems and Secure Execution

   - Some cleanups and refactorings, preparing for an upcoming big
     series

  x86:

   - Wait for target vCPU to ack KVM_REQ_UPDATE_PROTECTED_GUEST_STATE
     to fix a race between AP destroy and VMRUN

   - Decrypt and dump the VMSA in dump_vmcb() if debugging enabled for
     the VM

   - Refine and harden handling of spurious faults

   - Add support for ALLOWED_SEV_FEATURES

   - Add #VMGEXIT to the set of handlers special cased for
     CONFIG_RETPOLINE=y

   - Treat DEBUGCTL[5:2] as reserved to pave the way for virtualizing
     features that utilize those bits

   - Don't account temporary allocations in sev_send_update_data()

   - Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM, via Bus Lock
     Threshold

   - Unify virtualization of IBRS on nested VM-Exit, and cross-vCPU
     IBPB, between SVM and VMX

   - Advertise support to userspace for WRMSRNS and PREFETCHI

   - Rescan I/O APIC routes after handling EOI that needed to be
     intercepted due to the old/previous routing, but not the
     new/current routing

   - Add a module param to control and enumerate support for device
     posted interrupts

   - Fix a potential overflow with nested virt on Intel systems running
     32-bit kernels

   - Flush shadow VMCSes on emergency reboot

   - Add support for SNP to the various SEV selftests

   - Add a selftest to verify fastops instructions via forced emulation

   - Refine and optimize KVM's software processing of the posted
     interrupt bitmap, and share the harvesting code between KVM and the
     kernel's Posted MSI handler"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (93 commits)
  rtmutex_api: provide correct extern functions
  KVM: arm64: vgic-debug: Avoid dereferencing NULL ITE pointer
  KVM: arm64: vgic-init: Plug vCPU vs. VGIC creation race
  KVM: arm64: Unmap vLPIs affected by changes to GSI routing information
  KVM: arm64: Resolve vLPI by host IRQ in vgic_v4_unset_forwarding()
  KVM: arm64: Protect vLPI translation with vgic_irq::irq_lock
  KVM: arm64: Use lock guard in vgic_v4_set_forwarding()
  KVM: arm64: Mask out non-VA bits from TLBI VA* on VNCR invalidation
  arm64: sysreg: Drag linux/kconfig.h to work around vdso build issue
  KVM: s390: Simplify and move pv code
  KVM: s390: Refactor and split some gmap helpers
  KVM: s390: Remove unneeded srcu lock
  s390: Remove unneeded includes
  s390/uv: Improve splitting of large folios that cannot be split while dirty
  s390/uv: Always return 0 from s390_wiggle_split_folio() if successful
  s390/uv: Don't return 0 from make_hva_secure() if the operation was not successful
  rust: add helper for mutex_trylock
  RISC-V: KVM: use kvm_trylock_all_vcpus when locking all vCPUs
  KVM: arm64: use kvm_trylock_all_vcpus when locking all vCPUs
  x86: KVM: SVM: use kvm_lock_all_vcpus instead of a custom implementation
  ...
rtmutex_api: provide correct extern functions 2025-06-02T07:05:09+00:00 Paolo Bonzini pbonzini@redhat.com 2025-05-30T07:45:13+00:00 438e22801b1958f86883812af70d402eda29c4f5 Commit fb49f07ba1d9 ("locking/mutex: implement mutex_lock_killable_nest_lock") changed the set of functions that mutex.c defines when CONFIG_DEBUG_LOCK_ALLOC is set. - it removed the "extern" declaration of mutex_lock_killable_nested from include/linux/mutex.h, and replaced it with a macro since it could be treated as a special case of _mutex_lock_killable. It also removed a definition of the function in kernel/locking/mutex.c. - likewise, it replaced mutex_trylock() with the more generic mutex_trylock_nest_lock() and replaced mutex_trylock() with a macro. However, it left the old definitions in place in kernel/locking/rtmutex_api.c, which causes failures when building with CONFIG_RT_MUTEXES=y. Bring over the changes. Fixes: fb49f07ba1d9 ("locking/mutex: implement mutex_lock_killable_nest_lock") Reported-by: Randy Dunlap <rdunlap@infradead.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> 
Commit fb49f07ba1d9 ("locking/mutex: implement mutex_lock_killable_nest_lock")
changed the set of functions that mutex.c defines when CONFIG_DEBUG_LOCK_ALLOC
is set.

- it removed the "extern" declaration of mutex_lock_killable_nested from
  include/linux/mutex.h, and replaced it with a macro since it could be
  treated as a special case of _mutex_lock_killable.  It also removed a
  definition of the function in kernel/locking/mutex.c.

- likewise, it replaced mutex_trylock() with the more generic
  mutex_trylock_nest_lock() and replaced mutex_trylock() with a macro.

However, it left the old definitions in place in kernel/locking/rtmutex_api.c,
which causes failures when building with CONFIG_RT_MUTEXES=y.  Bring over
the changes.

Fixes: fb49f07ba1d9 ("locking/mutex: implement mutex_lock_killable_nest_lock")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Merge tag 'mm-nonmm-stable-2025-05-31-15-28' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 2025-06-01T02:12:53+00:00 Linus Torvalds torvalds@linux-foundation.org 2025-06-01T02:12:53+00:00 7d4e49a77d9930c69751b9192448fda6ff9100f1 Pull non-MM updates from Andrew Morton: - "hung_task: extend blocking task stacktrace dump to semaphore" from Lance Yang enhances the hung task detector. The detector presently dumps the blocking tasks's stack when it is blocked on a mutex. Lance's series extends this to semaphores - "nilfs2: improve sanity checks in dirty state propagation" from Wentao Liang addresses a couple of minor flaws in nilfs2 - "scripts/gdb: Fixes related to lx_per_cpu()" from Illia Ostapyshyn fixes a couple of issues in the gdb scripts - "Support kdump with LUKS encryption by reusing LUKS volume keys" from Coiby Xu addresses a usability problem with kdump. When the dump device is LUKS-encrypted, the kdump kernel may not have the keys to the encrypted filesystem. A full writeup of this is in the series [0/N] cover letter - "sysfs: add counters for lockups and stalls" from Max Kellermann adds /sys/kernel/hardlockup_count and /sys/kernel/hardlockup_count and /sys/kernel/rcu_stall_count - "fork: Page operation cleanups in the fork code" from Pasha Tatashin implements a number of code cleanups in fork.c - "scripts/gdb/symbols: determine KASLR offset on s390 during early boot" from Ilya Leoshkevich fixes some s390 issues in the gdb scripts * tag 'mm-nonmm-stable-2025-05-31-15-28' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (67 commits) llist: make llist_add_batch() a static inline delayacct: remove redundant code and adjust indentation squashfs: add optional full compressed block caching crash_dump, nvme: select CONFIGFS_FS as built-in scripts/gdb/symbols: determine KASLR offset on s390 during early boot scripts/gdb/symbols: factor out pagination_off() scripts/gdb/symbols: factor out get_vmlinux() kernel/panic.c: format kernel-doc comments mailmap: update and consolidate Casey Connolly's name and email nilfs2: remove wbc->for_reclaim handling fork: define a local GFP_VMAP_STACK fork: check charging success before zeroing stack fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code fork: clean-up ifdef logic around stack allocation kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count kernel/watchdog: add /sys/kernel/{hard,soft}lockup_count x86/crash: make the page that stores the dm crypt keys inaccessible x86/crash: pass dm crypt keys to kdump kernel Revert "x86/mm: Remove unused __set_memory_prot()" crash_dump: retrieve dm crypt keys in kdump kernel ... 
Pull non-MM updates from Andrew Morton:

 - "hung_task: extend blocking task stacktrace dump to semaphore" from
   Lance Yang enhances the hung task detector.

   The detector presently dumps the blocking tasks's stack when it is
   blocked on a mutex. Lance's series extends this to semaphores

 - "nilfs2: improve sanity checks in dirty state propagation" from
   Wentao Liang addresses a couple of minor flaws in nilfs2

 - "scripts/gdb: Fixes related to lx_per_cpu()" from Illia Ostapyshyn
   fixes a couple of issues in the gdb scripts

 - "Support kdump with LUKS encryption by reusing LUKS volume keys" from
   Coiby Xu addresses a usability problem with kdump.

   When the dump device is LUKS-encrypted, the kdump kernel may not have
   the keys to the encrypted filesystem. A full writeup of this is in
   the series [0/N] cover letter

 - "sysfs: add counters for lockups and stalls" from Max Kellermann adds
   /sys/kernel/hardlockup_count and /sys/kernel/hardlockup_count and
   /sys/kernel/rcu_stall_count

 - "fork: Page operation cleanups in the fork code" from Pasha Tatashin
   implements a number of code cleanups in fork.c

 - "scripts/gdb/symbols: determine KASLR offset on s390 during early
   boot" from Ilya Leoshkevich fixes some s390 issues in the gdb
   scripts

* tag 'mm-nonmm-stable-2025-05-31-15-28' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (67 commits)
  llist: make llist_add_batch() a static inline
  delayacct: remove redundant code and adjust indentation
  squashfs: add optional full compressed block caching
  crash_dump, nvme: select CONFIGFS_FS as built-in
  scripts/gdb/symbols: determine KASLR offset on s390 during early boot
  scripts/gdb/symbols: factor out pagination_off()
  scripts/gdb/symbols: factor out get_vmlinux()
  kernel/panic.c: format kernel-doc comments
  mailmap: update and consolidate Casey Connolly's name and email
  nilfs2: remove wbc->for_reclaim handling
  fork: define a local GFP_VMAP_STACK
  fork: check charging success before zeroing stack
  fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code
  fork: clean-up ifdef logic around stack allocation
  kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count
  kernel/watchdog: add /sys/kernel/{hard,soft}lockup_count
  x86/crash: make the page that stores the dm crypt keys inaccessible
  x86/crash: pass dm crypt keys to kdump kernel
  Revert "x86/mm: Remove unused __set_memory_prot()"
  crash_dump: retrieve dm crypt keys in kdump kernel
  ...
locking/mutex: implement mutex_lock_killable_nest_lock 2025-05-27T16:16:41+00:00 Maxim Levitsky mlevitsk@redhat.com 2025-05-12T18:04:03+00:00 fb49f07ba1d9d8c9bd8854878ae6b5b21ff9ac45 KVM's SEV intra-host migration code needs to lock all vCPUs of the source and the target VM, before it proceeds with the migration. The number of vCPUs that belong to each VM is not bounded by anything except a self-imposed KVM limit of CONFIG_KVM_MAX_NR_VCPUS vCPUs which is significantly larger than the depth of lockdep's lock stack. Luckily, the locks in both of the cases mentioned above, are held under the 'kvm->lock' of each VM, which means that we can use the little known lockdep feature called a "nest_lock" to support this use case in a cleaner way, compared to the way it's currently done. Implement and expose 'mutex_lock_killable_nest_lock' for this purpose. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Message-ID: <20250512180407.659015-3-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> 
KVM's SEV intra-host migration code needs to lock all vCPUs
of the source and the target VM, before it proceeds with the migration.

The number of vCPUs that belong to each VM is not bounded by anything
except a self-imposed KVM limit of CONFIG_KVM_MAX_NR_VCPUS vCPUs which is
significantly larger than the depth of lockdep's lock stack.

Luckily, the locks in both of the cases mentioned above, are held under
the 'kvm->lock' of each VM, which means that we can use the little
known lockdep feature called a "nest_lock" to support this use case in
a cleaner way, compared to the way it's currently done.

Implement and expose 'mutex_lock_killable_nest_lock' for this
purpose.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Message-ID: <20250512180407.659015-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
locking/mutex: implement mutex_trylock_nested 2025-05-27T16:16:40+00:00 Maxim Levitsky mlevitsk@redhat.com 2025-05-12T18:04:02+00:00 c5b6ababd21ab6bb251e5a2b4db110e76fb00a26 Despite the fact that several lockdep-related checks are skipped when calling trylock* versions of the locking primitives, for example mutex_trylock, each time the mutex is acquired, a held_lock is still placed onto the lockdep stack by __lock_acquire() which is called regardless of whether the trylock* or regular locking API was used. This means that if the caller successfully acquires more than MAX_LOCK_DEPTH locks of the same class, even when using mutex_trylock, lockdep will still complain that the maximum depth of the held lock stack has been reached and disable itself. For example, the following error currently occurs in the ARM version of KVM, once the code tries to lock all vCPUs of a VM configured with more than MAX_LOCK_DEPTH vCPUs, a situation that can easily happen on modern systems, where having more than 48 CPUs is common, and it's also common to run VMs that have vCPU counts approaching that number: [ 328.171264] BUG: MAX_LOCK_DEPTH too low! [ 328.175227] turning off the locking correctness validator. [ 328.180726] Please attach the output of /proc/lock_stat to the bug report [ 328.187531] depth: 48 max: 48! [ 328.190678] 48 locks held by qemu-kvm/11664: [ 328.194957] #0: ffff800086de5ba0 (&kvm->lock){+.+.}-{3:3}, at: kvm_ioctl_create_device+0x174/0x5b0 [ 328.204048] #1: ffff0800e78800b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.212521] #2: ffff07ffeee51e98 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.220991] #3: ffff0800dc7d80b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.229463] #4: ffff07ffe0c980b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.237934] #5: ffff0800a3883c78 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 [ 328.246405] #6: ffff07fffbe480b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0 Luckily, in all instances that require locking all vCPUs, the 'kvm->lock' is taken a priori, and that fact makes it possible to use the little known feature of lockdep, called a 'nest_lock', to avoid this warning and subsequent lockdep self-disablement. The action of 'nested lock' being provided to lockdep's lock_acquire(), causes the lockdep to detect that the top of the held lock stack contains a lock of the same class and then increment its reference counter instead of pushing a new held_lock item onto that stack. See __lock_acquire for more information. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Message-ID: <20250512180407.659015-2-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> 
Despite the fact that several lockdep-related checks are skipped when
calling trylock* versions of the locking primitives, for example
mutex_trylock, each time the mutex is acquired, a held_lock is still
placed onto the lockdep stack by __lock_acquire() which is called
regardless of whether the trylock* or regular locking API was used.

This means that if the caller successfully acquires more than
MAX_LOCK_DEPTH locks of the same class, even when using mutex_trylock,
lockdep will still complain that the maximum depth of the held lock stack
has been reached and disable itself.

For example, the following error currently occurs in the ARM version
of KVM, once the code tries to lock all vCPUs of a VM configured with more
than MAX_LOCK_DEPTH vCPUs, a situation that can easily happen on modern
systems, where having more than 48 CPUs is common, and it's also common to
run VMs that have vCPU counts approaching that number:

[  328.171264] BUG: MAX_LOCK_DEPTH too low!
[  328.175227] turning off the locking correctness validator.
[  328.180726] Please attach the output of /proc/lock_stat to the bug report
[  328.187531] depth: 48  max: 48!
[  328.190678] 48 locks held by qemu-kvm/11664:
[  328.194957]  #0: ffff800086de5ba0 (&kvm->lock){+.+.}-{3:3}, at: kvm_ioctl_create_device+0x174/0x5b0
[  328.204048]  #1: ffff0800e78800b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.212521]  #2: ffff07ffeee51e98 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.220991]  #3: ffff0800dc7d80b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.229463]  #4: ffff07ffe0c980b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.237934]  #5: ffff0800a3883c78 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.246405]  #6: ffff07fffbe480b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0

Luckily, in all instances that require locking all vCPUs, the
'kvm->lock' is taken a priori, and that fact makes it possible to use
the little known feature of lockdep, called a 'nest_lock', to avoid this
warning and subsequent lockdep self-disablement.

The action of 'nested lock' being provided to lockdep's lock_acquire(),
causes the lockdep to detect that the top of the held lock stack contains
a lock of the same class and then increment its reference counter instead
of pushing a new held_lock item onto that stack.

See __lock_acquire for more information.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Message-ID: <20250512180407.659015-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Merge tag 'locking-core-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2025-05-26T21:42:07+00:00 Linus Torvalds torvalds@linux-foundation.org 2025-05-26T21:42:07+00:00 b3570b00dc3062c5a5e8d9602b923618d679636a Pull locking updates from Ingo Molnar: "Futexes: - Add support for task local hash maps (Sebastian Andrzej Siewior, Peter Zijlstra) - Implement the FUTEX2_NUMA ABI, which feature extends the futex interface to be NUMA-aware. On NUMA-aware futexes a second u32 word containing the NUMA node is added to after the u32 futex value word (Peter Zijlstra) - Implement the FUTEX2_MPOL ABI, which feature extends the futex interface to be mempolicy-aware as well, to further refine futex node mappings and lookups (Peter Zijlstra) Locking primitives: - Misc cleanups (Andy Shevchenko, Borislav Petkov, Colin Ian King, Ingo Molnar, Nam Cao, Peter Zijlstra) Lockdep: - Prevent abuse of lockdep subclasses (Waiman Long) - Add number of dynamic keys to /proc/lockdep_stats (Waiman Long) Plus misc cleanups and fixes" * tag 'locking-core-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (35 commits) selftests/futex: Fix spelling mistake "unitiliazed" -> "uninitialized" futex: Correct the kernedoc return value for futex_wait_setup(). tools headers: Synchronize prctl.h ABI header futex: Use RCU_INIT_POINTER() in futex_mm_init(). selftests/futex: Use TAP output in futex_numa_mpol selftests/futex: Use TAP output in futex_priv_hash futex: Fix kernel-doc comments futex: Relax the rcu_assign_pointer() assignment of mm->futex_phash in futex_mm_init() futex: Fix outdated comment in struct restart_block locking/lockdep: Add number of dynamic keys to /proc/lockdep_stats locking/lockdep: Prevent abuse of lockdep subclass locking/lockdep: Move hlock_equal() to the respective #ifdeffery futex,selftests: Add another FUTEX2_NUMA selftest selftests/futex: Add futex_numa_mpol selftests/futex: Add futex_priv_hash selftests/futex: Build without headers nonsense tools/perf: Allow to select the number of hash buckets tools headers: Synchronize prctl.h ABI header futex: Implement FUTEX2_MPOL futex: Implement FUTEX2_NUMA ... 
Pull locking updates from Ingo Molnar:
 "Futexes:

   - Add support for task local hash maps (Sebastian Andrzej Siewior,
     Peter Zijlstra)

   - Implement the FUTEX2_NUMA ABI, which feature extends the futex
     interface to be NUMA-aware. On NUMA-aware futexes a second u32 word
     containing the NUMA node is added to after the u32 futex value word
     (Peter Zijlstra)

   - Implement the FUTEX2_MPOL ABI, which feature extends the futex
     interface to be mempolicy-aware as well, to further refine futex
     node mappings and lookups (Peter Zijlstra)

  Locking primitives:

   - Misc cleanups (Andy Shevchenko, Borislav Petkov, Colin Ian King,
     Ingo Molnar, Nam Cao, Peter Zijlstra)

  Lockdep:

   - Prevent abuse of lockdep subclasses (Waiman Long)

   - Add number of dynamic keys to /proc/lockdep_stats (Waiman Long)

  Plus misc cleanups and fixes"

* tag 'locking-core-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (35 commits)
  selftests/futex: Fix spelling mistake "unitiliazed" -> "uninitialized"
  futex: Correct the kernedoc return value for futex_wait_setup().
  tools headers: Synchronize prctl.h ABI header
  futex: Use RCU_INIT_POINTER() in futex_mm_init().
  selftests/futex: Use TAP output in futex_numa_mpol
  selftests/futex: Use TAP output in futex_priv_hash
  futex: Fix kernel-doc comments
  futex: Relax the rcu_assign_pointer() assignment of mm->futex_phash in futex_mm_init()
  futex: Fix outdated comment in struct restart_block
  locking/lockdep: Add number of dynamic keys to /proc/lockdep_stats
  locking/lockdep: Prevent abuse of lockdep subclass
  locking/lockdep: Move hlock_equal() to the respective #ifdeffery
  futex,selftests: Add another FUTEX2_NUMA selftest
  selftests/futex: Add futex_numa_mpol
  selftests/futex: Add futex_priv_hash
  selftests/futex: Build without headers nonsense
  tools/perf: Allow to select the number of hash buckets
  tools headers: Synchronize prctl.h ABI header
  futex: Implement FUTEX2_MPOL
  futex: Implement FUTEX2_NUMA
  ...
hung_task: show the blocker task if the task is hung on semaphore 2025-05-12T00:54:08+00:00 Lance Yang ioworker0@gmail.com 2025-04-14T14:59:44+00:00 194a9b9e843b4077033be70a07d191107972aa53 Inspired by mutex blocker tracking[1], this patch makes a trade-off to balance the overhead and utility of the hung task detector. Unlike mutexes, semaphores lack explicit ownership tracking, making it challenging to identify the root cause of hangs. To address this, we introduce a last_holder field to the semaphore structure, which is updated when a task successfully calls down() and cleared during up(). The assumption is that if a task is blocked on a semaphore, the holders must not have released it. While this does not guarantee that the last holder is one of the current blockers, it likely provides a practical hint for diagnosing semaphore-related stalls. With this change, the hung task detector can now show blocker task's info like below: [Tue Apr 8 12:19:07 2025] INFO: task cat:945 blocked for more than 120 seconds. [Tue Apr 8 12:19:07 2025] Tainted: G E 6.14.0-rc6+ #1 [Tue Apr 8 12:19:07 2025] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [Tue Apr 8 12:19:07 2025] task:cat state:D stack:0 pid:945 tgid:945 ppid:828 task_flags:0x400000 flags:0x00000000 [Tue Apr 8 12:19:07 2025] Call Trace: [Tue Apr 8 12:19:07 2025] <TASK> [Tue Apr 8 12:19:07 2025] __schedule+0x491/0xbd0 [Tue Apr 8 12:19:07 2025] schedule+0x27/0xf0 [Tue Apr 8 12:19:07 2025] schedule_timeout+0xe3/0xf0 [Tue Apr 8 12:19:07 2025] ? __folio_mod_stat+0x2a/0x80 [Tue Apr 8 12:19:07 2025] ? set_ptes.constprop.0+0x27/0x90 [Tue Apr 8 12:19:07 2025] __down_common+0x155/0x280 [Tue Apr 8 12:19:07 2025] down+0x53/0x70 [Tue Apr 8 12:19:07 2025] read_dummy_semaphore+0x23/0x60 [Tue Apr 8 12:19:07 2025] full_proxy_read+0x5f/0xa0 [Tue Apr 8 12:19:07 2025] vfs_read+0xbc/0x350 [Tue Apr 8 12:19:07 2025] ? __count_memcg_events+0xa5/0x140 [Tue Apr 8 12:19:07 2025] ? count_memcg_events.constprop.0+0x1a/0x30 [Tue Apr 8 12:19:07 2025] ? handle_mm_fault+0x180/0x260 [Tue Apr 8 12:19:07 2025] ksys_read+0x66/0xe0 [Tue Apr 8 12:19:07 2025] do_syscall_64+0x51/0x120 [Tue Apr 8 12:19:07 2025] entry_SYSCALL_64_after_hwframe+0x76/0x7e [Tue Apr 8 12:19:07 2025] RIP: 0033:0x7f419478f46e [Tue Apr 8 12:19:07 2025] RSP: 002b:00007fff1c4d2668 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [Tue Apr 8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f419478f46e [Tue Apr 8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f4194683000 RDI: 0000000000000003 [Tue Apr 8 12:19:07 2025] RBP: 00007f4194683000 R08: 00007f4194682010 R09: 0000000000000000 [Tue Apr 8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000 [Tue Apr 8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000 [Tue Apr 8 12:19:07 2025] </TASK> [Tue Apr 8 12:19:07 2025] INFO: task cat:945 blocked on a semaphore likely last held by task cat:938 [Tue Apr 8 12:19:07 2025] task:cat state:S stack:0 pid:938 tgid:938 ppid:584 task_flags:0x400000 flags:0x00000000 [Tue Apr 8 12:19:07 2025] Call Trace: [Tue Apr 8 12:19:07 2025] <TASK> [Tue Apr 8 12:19:07 2025] __schedule+0x491/0xbd0 [Tue Apr 8 12:19:07 2025] ? _raw_spin_unlock_irqrestore+0xe/0x40 [Tue Apr 8 12:19:07 2025] schedule+0x27/0xf0 [Tue Apr 8 12:19:07 2025] schedule_timeout+0x77/0xf0 [Tue Apr 8 12:19:07 2025] ? __pfx_process_timeout+0x10/0x10 [Tue Apr 8 12:19:07 2025] msleep_interruptible+0x49/0x60 [Tue Apr 8 12:19:07 2025] read_dummy_semaphore+0x2d/0x60 [Tue Apr 8 12:19:07 2025] full_proxy_read+0x5f/0xa0 [Tue Apr 8 12:19:07 2025] vfs_read+0xbc/0x350 [Tue Apr 8 12:19:07 2025] ? __count_memcg_events+0xa5/0x140 [Tue Apr 8 12:19:07 2025] ? count_memcg_events.constprop.0+0x1a/0x30 [Tue Apr 8 12:19:07 2025] ? handle_mm_fault+0x180/0x260 [Tue Apr 8 12:19:07 2025] ksys_read+0x66/0xe0 [Tue Apr 8 12:19:07 2025] do_syscall_64+0x51/0x120 [Tue Apr 8 12:19:07 2025] entry_SYSCALL_64_after_hwframe+0x76/0x7e [Tue Apr 8 12:19:07 2025] RIP: 0033:0x7f7c584a646e [Tue Apr 8 12:19:07 2025] RSP: 002b:00007ffdba8ce158 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [Tue Apr 8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f7c584a646e [Tue Apr 8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f7c5839a000 RDI: 0000000000000003 [Tue Apr 8 12:19:07 2025] RBP: 00007f7c5839a000 R08: 00007f7c58399010 R09: 0000000000000000 [Tue Apr 8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000 [Tue Apr 8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000 [Tue Apr 8 12:19:07 2025] </TASK> [1] https://lore.kernel.org/all/174046694331.2194069.15472952050240807469.stgit@mhiramat.tok.corp.google.com Link: https://lkml.kernel.org/r/20250414145945.84916-3-ioworker0@gmail.com Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com> Signed-off-by: Lance Yang <ioworker0@gmail.com> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Cc: Anna Schumaker <anna.schumaker@oracle.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joel Granados <joel.granados@kernel.org> Cc: John Stultz <jstultz@google.com> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tomasz Figa <tfiga@chromium.org> Cc: Waiman Long <longman@redhat.com> Cc: Will Deacon <will@kernel.org> Cc: Yongliang Gao <leonylgao@tencent.com> Cc: Zi Li <amaindex@outlook.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Inspired by mutex blocker tracking[1], this patch makes a trade-off to
balance the overhead and utility of the hung task detector.

Unlike mutexes, semaphores lack explicit ownership tracking, making it
challenging to identify the root cause of hangs.  To address this, we
introduce a last_holder field to the semaphore structure, which is updated
when a task successfully calls down() and cleared during up().

The assumption is that if a task is blocked on a semaphore, the holders
must not have released it.  While this does not guarantee that the last
holder is one of the current blockers, it likely provides a practical hint
for diagnosing semaphore-related stalls.

With this change, the hung task detector can now show blocker task's info
like below:

[Tue Apr  8 12:19:07 2025] INFO: task cat:945 blocked for more than 120 seconds.
[Tue Apr  8 12:19:07 2025]       Tainted: G            E      6.14.0-rc6+ #1
[Tue Apr  8 12:19:07 2025] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[Tue Apr  8 12:19:07 2025] task:cat             state:D stack:0     pid:945   tgid:945   ppid:828    task_flags:0x400000 flags:0x00000000
[Tue Apr  8 12:19:07 2025] Call Trace:
[Tue Apr  8 12:19:07 2025]  <TASK>
[Tue Apr  8 12:19:07 2025]  __schedule+0x491/0xbd0
[Tue Apr  8 12:19:07 2025]  schedule+0x27/0xf0
[Tue Apr  8 12:19:07 2025]  schedule_timeout+0xe3/0xf0
[Tue Apr  8 12:19:07 2025]  ? __folio_mod_stat+0x2a/0x80
[Tue Apr  8 12:19:07 2025]  ? set_ptes.constprop.0+0x27/0x90
[Tue Apr  8 12:19:07 2025]  __down_common+0x155/0x280
[Tue Apr  8 12:19:07 2025]  down+0x53/0x70
[Tue Apr  8 12:19:07 2025]  read_dummy_semaphore+0x23/0x60
[Tue Apr  8 12:19:07 2025]  full_proxy_read+0x5f/0xa0
[Tue Apr  8 12:19:07 2025]  vfs_read+0xbc/0x350
[Tue Apr  8 12:19:07 2025]  ? __count_memcg_events+0xa5/0x140
[Tue Apr  8 12:19:07 2025]  ? count_memcg_events.constprop.0+0x1a/0x30
[Tue Apr  8 12:19:07 2025]  ? handle_mm_fault+0x180/0x260
[Tue Apr  8 12:19:07 2025]  ksys_read+0x66/0xe0
[Tue Apr  8 12:19:07 2025]  do_syscall_64+0x51/0x120
[Tue Apr  8 12:19:07 2025]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[Tue Apr  8 12:19:07 2025] RIP: 0033:0x7f419478f46e
[Tue Apr  8 12:19:07 2025] RSP: 002b:00007fff1c4d2668 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[Tue Apr  8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f419478f46e
[Tue Apr  8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f4194683000 RDI: 0000000000000003
[Tue Apr  8 12:19:07 2025] RBP: 00007f4194683000 R08: 00007f4194682010 R09: 0000000000000000
[Tue Apr  8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000
[Tue Apr  8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
[Tue Apr  8 12:19:07 2025]  </TASK>
[Tue Apr  8 12:19:07 2025] INFO: task cat:945 blocked on a semaphore likely last held by task cat:938
[Tue Apr  8 12:19:07 2025] task:cat             state:S stack:0     pid:938   tgid:938   ppid:584    task_flags:0x400000 flags:0x00000000
[Tue Apr  8 12:19:07 2025] Call Trace:
[Tue Apr  8 12:19:07 2025]  <TASK>
[Tue Apr  8 12:19:07 2025]  __schedule+0x491/0xbd0
[Tue Apr  8 12:19:07 2025]  ? _raw_spin_unlock_irqrestore+0xe/0x40
[Tue Apr  8 12:19:07 2025]  schedule+0x27/0xf0
[Tue Apr  8 12:19:07 2025]  schedule_timeout+0x77/0xf0
[Tue Apr  8 12:19:07 2025]  ? __pfx_process_timeout+0x10/0x10
[Tue Apr  8 12:19:07 2025]  msleep_interruptible+0x49/0x60
[Tue Apr  8 12:19:07 2025]  read_dummy_semaphore+0x2d/0x60
[Tue Apr  8 12:19:07 2025]  full_proxy_read+0x5f/0xa0
[Tue Apr  8 12:19:07 2025]  vfs_read+0xbc/0x350
[Tue Apr  8 12:19:07 2025]  ? __count_memcg_events+0xa5/0x140
[Tue Apr  8 12:19:07 2025]  ? count_memcg_events.constprop.0+0x1a/0x30
[Tue Apr  8 12:19:07 2025]  ? handle_mm_fault+0x180/0x260
[Tue Apr  8 12:19:07 2025]  ksys_read+0x66/0xe0
[Tue Apr  8 12:19:07 2025]  do_syscall_64+0x51/0x120
[Tue Apr  8 12:19:07 2025]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[Tue Apr  8 12:19:07 2025] RIP: 0033:0x7f7c584a646e
[Tue Apr  8 12:19:07 2025] RSP: 002b:00007ffdba8ce158 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[Tue Apr  8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f7c584a646e
[Tue Apr  8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f7c5839a000 RDI: 0000000000000003
[Tue Apr  8 12:19:07 2025] RBP: 00007f7c5839a000 R08: 00007f7c58399010 R09: 0000000000000000
[Tue Apr  8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000
[Tue Apr  8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
[Tue Apr  8 12:19:07 2025]  </TASK>

[1] https://lore.kernel.org/all/174046694331.2194069.15472952050240807469.stgit@mhiramat.tok.corp.google.com

Link: https://lkml.kernel.org/r/20250414145945.84916-3-ioworker0@gmail.com
Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com>
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Anna Schumaker <anna.schumaker@oracle.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yongliang Gao <leonylgao@tencent.com>
Cc: Zi Li <amaindex@outlook.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
hung_task: replace blocker_mutex with encoded blocker 2025-05-12T00:54:07+00:00 Lance Yang ioworker0@gmail.com 2025-04-14T14:59:43+00:00 e711faaafbe54a884f33b53472434063d342f6d4 Patch series "hung_task: extend blocking task stacktrace dump to semaphore", v5. Inspired by mutex blocker tracking[1], this patch series extend the feature to not only dump the blocker task holding a mutex but also to support semaphores. Unlike mutexes, semaphores lack explicit ownership tracking, making it challenging to identify the root cause of hangs. To address this, we introduce a last_holder field to the semaphore structure, which is updated when a task successfully calls down() and cleared during up(). The assumption is that if a task is blocked on a semaphore, the holders must not have released it. While this does not guarantee that the last holder is one of the current blockers, it likely provides a practical hint for diagnosing semaphore-related stalls. With this change, the hung task detector can now show blocker task's info like below: [Tue Apr 8 12:19:07 2025] INFO: task cat:945 blocked for more than 120 seconds. [Tue Apr 8 12:19:07 2025] Tainted: G E 6.14.0-rc6+ #1 [Tue Apr 8 12:19:07 2025] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [Tue Apr 8 12:19:07 2025] task:cat state:D stack:0 pid:945 tgid:945 ppid:828 task_flags:0x400000 flags:0x00000000 [Tue Apr 8 12:19:07 2025] Call Trace: [Tue Apr 8 12:19:07 2025] <TASK> [Tue Apr 8 12:19:07 2025] __schedule+0x491/0xbd0 [Tue Apr 8 12:19:07 2025] schedule+0x27/0xf0 [Tue Apr 8 12:19:07 2025] schedule_timeout+0xe3/0xf0 [Tue Apr 8 12:19:07 2025] ? __folio_mod_stat+0x2a/0x80 [Tue Apr 8 12:19:07 2025] ? set_ptes.constprop.0+0x27/0x90 [Tue Apr 8 12:19:07 2025] __down_common+0x155/0x280 [Tue Apr 8 12:19:07 2025] down+0x53/0x70 [Tue Apr 8 12:19:07 2025] read_dummy_semaphore+0x23/0x60 [Tue Apr 8 12:19:07 2025] full_proxy_read+0x5f/0xa0 [Tue Apr 8 12:19:07 2025] vfs_read+0xbc/0x350 [Tue Apr 8 12:19:07 2025] ? __count_memcg_events+0xa5/0x140 [Tue Apr 8 12:19:07 2025] ? count_memcg_events.constprop.0+0x1a/0x30 [Tue Apr 8 12:19:07 2025] ? handle_mm_fault+0x180/0x260 [Tue Apr 8 12:19:07 2025] ksys_read+0x66/0xe0 [Tue Apr 8 12:19:07 2025] do_syscall_64+0x51/0x120 [Tue Apr 8 12:19:07 2025] entry_SYSCALL_64_after_hwframe+0x76/0x7e [Tue Apr 8 12:19:07 2025] RIP: 0033:0x7f419478f46e [Tue Apr 8 12:19:07 2025] RSP: 002b:00007fff1c4d2668 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [Tue Apr 8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f419478f46e [Tue Apr 8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f4194683000 RDI: 0000000000000003 [Tue Apr 8 12:19:07 2025] RBP: 00007f4194683000 R08: 00007f4194682010 R09: 0000000000000000 [Tue Apr 8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000 [Tue Apr 8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000 [Tue Apr 8 12:19:07 2025] </TASK> [Tue Apr 8 12:19:07 2025] INFO: task cat:945 blocked on a semaphore likely last held by task cat:938 [Tue Apr 8 12:19:07 2025] task:cat state:S stack:0 pid:938 tgid:938 ppid:584 task_flags:0x400000 flags:0x00000000 [Tue Apr 8 12:19:07 2025] Call Trace: [Tue Apr 8 12:19:07 2025] <TASK> [Tue Apr 8 12:19:07 2025] __schedule+0x491/0xbd0 [Tue Apr 8 12:19:07 2025] ? _raw_spin_unlock_irqrestore+0xe/0x40 [Tue Apr 8 12:19:07 2025] schedule+0x27/0xf0 [Tue Apr 8 12:19:07 2025] schedule_timeout+0x77/0xf0 [Tue Apr 8 12:19:07 2025] ? __pfx_process_timeout+0x10/0x10 [Tue Apr 8 12:19:07 2025] msleep_interruptible+0x49/0x60 [Tue Apr 8 12:19:07 2025] read_dummy_semaphore+0x2d/0x60 [Tue Apr 8 12:19:07 2025] full_proxy_read+0x5f/0xa0 [Tue Apr 8 12:19:07 2025] vfs_read+0xbc/0x350 [Tue Apr 8 12:19:07 2025] ? __count_memcg_events+0xa5/0x140 [Tue Apr 8 12:19:07 2025] ? count_memcg_events.constprop.0+0x1a/0x30 [Tue Apr 8 12:19:07 2025] ? handle_mm_fault+0x180/0x260 [Tue Apr 8 12:19:07 2025] ksys_read+0x66/0xe0 [Tue Apr 8 12:19:07 2025] do_syscall_64+0x51/0x120 [Tue Apr 8 12:19:07 2025] entry_SYSCALL_64_after_hwframe+0x76/0x7e [Tue Apr 8 12:19:07 2025] RIP: 0033:0x7f7c584a646e [Tue Apr 8 12:19:07 2025] RSP: 002b:00007ffdba8ce158 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [Tue Apr 8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f7c584a646e [Tue Apr 8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f7c5839a000 RDI: 0000000000000003 [Tue Apr 8 12:19:07 2025] RBP: 00007f7c5839a000 R08: 00007f7c58399010 R09: 0000000000000000 [Tue Apr 8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000 [Tue Apr 8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000 [Tue Apr 8 12:19:07 2025] </TASK> This patch (of 3): This patch replaces 'struct mutex *blocker_mutex' with 'unsigned long blocker', as only one blocker is active at a time. The blocker filed can store both the lock addrees and the lock type, with LSB used to encode the type as Masami suggested, making it easier to extend the feature to cover other types of locks. Also, once the lock type is determined, we can directly extract the address and cast it to a lock pointer ;) Link: https://lkml.kernel.org/r/20250414145945.84916-1-ioworker0@gmail.com Link: https://lore.kernel.org/all/174046694331.2194069.15472952050240807469.stgit@mhiramat.tok.corp.google.com [1] Link: https://lkml.kernel.org/r/20250414145945.84916-2-ioworker0@gmail.com Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com> Signed-off-by: Lance Yang <ioworker0@gmail.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Cc: Anna Schumaker <anna.schumaker@oracle.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joel Granados <joel.granados@kernel.org> Cc: John Stultz <jstultz@google.com> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tomasz Figa <tfiga@chromium.org> Cc: Waiman Long <longman@redhat.com> Cc: Will Deacon <will@kernel.org> Cc: Yongliang Gao <leonylgao@tencent.com> Cc: Zi Li <amaindex@outlook.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
Patch series "hung_task: extend blocking task stacktrace dump to
semaphore", v5.

Inspired by mutex blocker tracking[1], this patch series extend the
feature to not only dump the blocker task holding a mutex but also to
support semaphores.  Unlike mutexes, semaphores lack explicit ownership
tracking, making it challenging to identify the root cause of hangs.  To
address this, we introduce a last_holder field to the semaphore structure,
which is updated when a task successfully calls down() and cleared during
up().

The assumption is that if a task is blocked on a semaphore, the holders
must not have released it.  While this does not guarantee that the last
holder is one of the current blockers, it likely provides a practical hint
for diagnosing semaphore-related stalls.

With this change, the hung task detector can now show blocker task's info
like below:

[Tue Apr  8 12:19:07 2025] INFO: task cat:945 blocked for more than 120 seconds.
[Tue Apr  8 12:19:07 2025]       Tainted: G            E      6.14.0-rc6+ #1
[Tue Apr  8 12:19:07 2025] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[Tue Apr  8 12:19:07 2025] task:cat             state:D stack:0     pid:945   tgid:945   ppid:828    task_flags:0x400000 flags:0x00000000
[Tue Apr  8 12:19:07 2025] Call Trace:
[Tue Apr  8 12:19:07 2025]  <TASK>
[Tue Apr  8 12:19:07 2025]  __schedule+0x491/0xbd0
[Tue Apr  8 12:19:07 2025]  schedule+0x27/0xf0
[Tue Apr  8 12:19:07 2025]  schedule_timeout+0xe3/0xf0
[Tue Apr  8 12:19:07 2025]  ? __folio_mod_stat+0x2a/0x80
[Tue Apr  8 12:19:07 2025]  ? set_ptes.constprop.0+0x27/0x90
[Tue Apr  8 12:19:07 2025]  __down_common+0x155/0x280
[Tue Apr  8 12:19:07 2025]  down+0x53/0x70
[Tue Apr  8 12:19:07 2025]  read_dummy_semaphore+0x23/0x60
[Tue Apr  8 12:19:07 2025]  full_proxy_read+0x5f/0xa0
[Tue Apr  8 12:19:07 2025]  vfs_read+0xbc/0x350
[Tue Apr  8 12:19:07 2025]  ? __count_memcg_events+0xa5/0x140
[Tue Apr  8 12:19:07 2025]  ? count_memcg_events.constprop.0+0x1a/0x30
[Tue Apr  8 12:19:07 2025]  ? handle_mm_fault+0x180/0x260
[Tue Apr  8 12:19:07 2025]  ksys_read+0x66/0xe0
[Tue Apr  8 12:19:07 2025]  do_syscall_64+0x51/0x120
[Tue Apr  8 12:19:07 2025]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[Tue Apr  8 12:19:07 2025] RIP: 0033:0x7f419478f46e
[Tue Apr  8 12:19:07 2025] RSP: 002b:00007fff1c4d2668 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[Tue Apr  8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f419478f46e
[Tue Apr  8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f4194683000 RDI: 0000000000000003
[Tue Apr  8 12:19:07 2025] RBP: 00007f4194683000 R08: 00007f4194682010 R09: 0000000000000000
[Tue Apr  8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000
[Tue Apr  8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
[Tue Apr  8 12:19:07 2025]  </TASK>
[Tue Apr  8 12:19:07 2025] INFO: task cat:945 blocked on a semaphore likely last held by task cat:938
[Tue Apr  8 12:19:07 2025] task:cat             state:S stack:0     pid:938   tgid:938   ppid:584    task_flags:0x400000 flags:0x00000000
[Tue Apr  8 12:19:07 2025] Call Trace:
[Tue Apr  8 12:19:07 2025]  <TASK>
[Tue Apr  8 12:19:07 2025]  __schedule+0x491/0xbd0
[Tue Apr  8 12:19:07 2025]  ? _raw_spin_unlock_irqrestore+0xe/0x40
[Tue Apr  8 12:19:07 2025]  schedule+0x27/0xf0
[Tue Apr  8 12:19:07 2025]  schedule_timeout+0x77/0xf0
[Tue Apr  8 12:19:07 2025]  ? __pfx_process_timeout+0x10/0x10
[Tue Apr  8 12:19:07 2025]  msleep_interruptible+0x49/0x60
[Tue Apr  8 12:19:07 2025]  read_dummy_semaphore+0x2d/0x60
[Tue Apr  8 12:19:07 2025]  full_proxy_read+0x5f/0xa0
[Tue Apr  8 12:19:07 2025]  vfs_read+0xbc/0x350
[Tue Apr  8 12:19:07 2025]  ? __count_memcg_events+0xa5/0x140
[Tue Apr  8 12:19:07 2025]  ? count_memcg_events.constprop.0+0x1a/0x30
[Tue Apr  8 12:19:07 2025]  ? handle_mm_fault+0x180/0x260
[Tue Apr  8 12:19:07 2025]  ksys_read+0x66/0xe0
[Tue Apr  8 12:19:07 2025]  do_syscall_64+0x51/0x120
[Tue Apr  8 12:19:07 2025]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[Tue Apr  8 12:19:07 2025] RIP: 0033:0x7f7c584a646e
[Tue Apr  8 12:19:07 2025] RSP: 002b:00007ffdba8ce158 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[Tue Apr  8 12:19:07 2025] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f7c584a646e
[Tue Apr  8 12:19:07 2025] RDX: 0000000000020000 RSI: 00007f7c5839a000 RDI: 0000000000000003
[Tue Apr  8 12:19:07 2025] RBP: 00007f7c5839a000 R08: 00007f7c58399010 R09: 0000000000000000
[Tue Apr  8 12:19:07 2025] R10: fffffffffffffbc5 R11: 0000000000000246 R12: 0000000000000000
[Tue Apr  8 12:19:07 2025] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
[Tue Apr  8 12:19:07 2025]  </TASK>


This patch (of 3):

This patch replaces 'struct mutex *blocker_mutex' with 'unsigned long
blocker', as only one blocker is active at a time.

The blocker filed can store both the lock addrees and the lock type, with
LSB used to encode the type as Masami suggested, making it easier to
extend the feature to cover other types of locks.

Also, once the lock type is determined, we can directly extract the
address and cast it to a lock pointer ;)

Link: https://lkml.kernel.org/r/20250414145945.84916-1-ioworker0@gmail.com
Link: https://lore.kernel.org/all/174046694331.2194069.15472952050240807469.stgit@mhiramat.tok.corp.google.com [1]
Link: https://lkml.kernel.org/r/20250414145945.84916-2-ioworker0@gmail.com
Signed-off-by: Mingzhe Yang <mingzhe.yang@ly.com>
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Anna Schumaker <anna.schumaker@oracle.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: John Stultz <jstultz@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yongliang Gao <leonylgao@tencent.com>
Cc: Zi Li <amaindex@outlook.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
locking/lockdep: Add number of dynamic keys to /proc/lockdep_stats 2025-05-06T16:34:43+00:00 Waiman Long longman@redhat.com 2025-05-06T04:20:49+00:00 cdb7d2d68cde6145a06a56c9d5d5d917297501c6 There have been recent reports about running out of lockdep keys: MAX_LOCKDEP_KEYS too low! One possible reason is that too many dynamic keys have been registered. A possible culprit is the lockdep_register_key() call in qdisc_alloc() of net/sched/sch_generic.c. Currently, there is no way to find out how many dynamic keys have been registered. Add such a stat to the /proc/lockdep_stats to get better clarity. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20250506042049.50060-4-boqun.feng@gmail.com 
There have been recent reports about running out of lockdep keys:

	MAX_LOCKDEP_KEYS too low!

One possible reason is that too many dynamic keys have been registered.
A possible culprit is the lockdep_register_key() call in qdisc_alloc()
of net/sched/sch_generic.c.

Currently, there is no way to find out how many dynamic keys have been
registered. Add such a stat to the /proc/lockdep_stats to get better
clarity.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20250506042049.50060-4-boqun.feng@gmail.com
locking/lockdep: Prevent abuse of lockdep subclass 2025-05-06T16:34:35+00:00 Waiman Long longman@redhat.com 2025-05-06T04:20:48+00:00 6a1a219f535a437eb12a06d8cef2518e58654beb To catch the code trying to use a subclass value >= MAX_LOCKDEP_SUBCLASSES (8), add a DEBUG_LOCKS_WARN_ON() statement to notify the users that such a large value is not allowed. [ boqun: Reword the commit log with a more objective tone ] Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20250506042049.50060-3-boqun.feng@gmail.com 
To catch the code trying to use a subclass value >= MAX_LOCKDEP_SUBCLASSES (8),
add a DEBUG_LOCKS_WARN_ON() statement to notify the users that such a
large value is not allowed.

[ boqun: Reword the commit log with a more objective tone ]

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20250506042049.50060-3-boqun.feng@gmail.com