From 1b93c03fb319d72a1f5f4723abd5df15ce40f4e2 Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Thu, 21 Aug 2025 17:06:03 +0800 Subject: rcu: add rcu_read_lock_dont_migrate() migrate_disable() is called to disable migration in the kernel, and it is often used together with rcu_read_lock(). However, with PREEMPT_RCU disabled, it's unnecessary, as rcu_read_lock() will always disable preemption, which will also disable migration. Introduce rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate(), which will do the migration enable and disable only when PREEMPT_RCU. Signed-off-by: Menglong Dong Reviewed-by: Paul E. McKenney Link: https://lore.kernel.org/r/20250821090609.42508-2-dongml2@chinatelecom.cn Signed-off-by: Alexei Starovoitov --- include/linux/rcupdate.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..9691ca380a4f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -962,6 +962,20 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) preempt_enable_notrace(); } +static __always_inline void rcu_read_lock_dont_migrate(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_disable(); + rcu_read_lock(); +} + +static inline void rcu_read_unlock_migrate(void) +{ + rcu_read_unlock(); + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) + migrate_enable(); +} + /** * RCU_INIT_POINTER() - initialize an RCU protected pointer * @p: The pointer to be initialized. -- cgit v1.2.3 From bee8a520eb84950193d0566ea2c2e46406a4b6ce Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Tue, 9 Sep 2025 17:50:56 +0800 Subject: rhashtable: Use rcu_dereference_all and rcu_dereference_all_check Add rcu_dereference_all and rcu_dereference_all_check so that library code such as rhashtable can be used with any RCU variant. As it stands rcu_dereference is used within rashtable, which creates false-positive warnings if the user calls it from another RCU context, such as preempt_disable(). Use the rcu_dereference_all and rcu_dereference_all_check calls in rhashtable to suppress these warnings. Also replace the rcu_dereference_raw calls in the list iterators with rcu_dereference_all to uncover buggy calls. Reported-by: Menglong Dong Signed-off-by: Herbert Xu Reviewed-by: Paul E. McKenney Signed-off-by: Herbert Xu --- include/linux/rcupdate.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..448eb1f0cb48 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -713,6 +713,24 @@ do { \ (c) || rcu_read_lock_sched_held(), \ __rcu) +/** + * rcu_dereference_all_check() - rcu_dereference_all with debug checking + * @p: The pointer to read, prior to dereferencing + * @c: The conditions under which the dereference will take place + * + * This is similar to rcu_dereference_check(), but allows protection + * by all forms of vanilla RCU readers, including preemption disabled, + * bh-disabled, and interrupt-disabled regions of code. Note that "vanilla + * RCU" excludes SRCU and the various Tasks RCU flavors. Please note + * that this macro should not be backported to any Linux-kernel version + * preceding v5.0 due to changes in synchronize_rcu() semantics prior + * to that version. + */ +#define rcu_dereference_all_check(p, c) \ + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ + (c) || rcu_read_lock_any_held(), \ + __rcu) + /* * The tracing infrastructure traces RCU (we want that), but unfortunately * some of the RCU checks causes tracing to lock up the system. @@ -767,6 +785,14 @@ do { \ */ #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) +/** + * rcu_dereference_all() - fetch RCU-all-protected pointer for dereferencing + * @p: The pointer to read, prior to dereferencing + * + * Makes rcu_dereference_check() do the dirty work. + */ +#define rcu_dereference_all(p) rcu_dereference_all_check(p, 0) + /** * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism * @p: The pointer to hand off -- cgit v1.2.3 From 88a90315a99a9120cd471bf681515cc77cd7cdb8 Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Wed, 17 Sep 2025 14:09:14 +0800 Subject: rcu: Replace preempt.h with sched.h in include/linux/rcupdate.h In the next commit, we will move the definition of migrate_enable() and migrate_disable() to linux/sched.h. However, migrate_enable/migrate_disable will be used in commit 1b93c03fb319 ("rcu: add rcu_read_lock_dont_migrate()") in bpf-next tree. In order to fix potential compiling error, replace linux/preempt.h with linux/sched.h in include/linux/rcupdate.h. Signed-off-by: Menglong Dong Signed-off-by: Peter Zijlstra (Intel) --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..8f346c847ee5 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -24,7 +24,7 @@ #include #include #include -#include +#include #include #include #include -- cgit v1.2.3 From 9be7e1e320ff2e7db4b23c8ec5f599bbfac94ede Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 27 Aug 2025 17:01:54 -0700 Subject: entry: Rename "kvm" entry code assets to "virt" to genericize APIs Rename the "kvm" entry code files and Kconfigs to use generic "virt" nomenclature so that the code can be reused by other hypervisors (or rather, their root/dom0 partition drivers), without incorrectly suggesting the code somehow relies on and/or involves KVM. No functional change intended. Signed-off-by: Sean Christopherson Reviewed-by: Thomas Gleixner Reviewed-by: Joel Fernandes Signed-off-by: Wei Liu --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/rcupdate.h') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 120536f4c6eb..1e1f3aa375d9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -129,7 +129,7 @@ static inline void rcu_sysrq_start(void) { } static inline void rcu_sysrq_end(void) { } #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ -#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) +#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_VIRT_XFER_TO_GUEST_WORK)) void rcu_irq_work_resched(void); #else static __always_inline void rcu_irq_work_resched(void) { } -- cgit v1.2.3