linux-toradex.git/arch/mips/kernel/smp.c, branch v6.7

mips/smp: Call rcutree_report_cpu_starting() earlier

2023-12-05T17:43:05+00:00

rcutree_report_cpu_starting() must be called before
clockevents_register_device() to avoid the following lockdep splat triggered by
calling list_add() when CONFIG_PROVE_RCU_LIST=y:

  WARNING: suspicious RCU usage
  ...
  -----------------------------
  kernel/locking/lockdep.c:3680 RCU-list traversed in non-reader section!!

  other info that might help us debug this:

  RCU used illegally from offline CPU!
  rcu_scheduler_active = 1, debug_locks = 1
  no locks held by swapper/1/0.
  ...
  Call Trace:
  [] show_stack+0x64/0x158
  [] dump_stack_lvl+0x90/0xc4
  [] __lock_acquire+0x1404/0x2940
  [] lock_acquire+0x14c/0x448
  [] _raw_spin_lock_irqsave+0x50/0x88
  [] clockevents_register_device+0x60/0x1e8
  [] r4k_clockevent_init+0x220/0x3a0
  [] start_secondary+0x50/0x3b8

raw_smp_processor_id() is required in order to avoid calling into lockdep
before RCU has declared the CPU to be watched for readers.

See also commit 29368e093921 ("x86/smpboot:  Move rcu_cpu_starting() earlier"),
commit de5d9dae150c ("s390/smp: move rcu_cpu_starting() earlier") and commit
99f070b62322 ("powerpc/smp: Call rcu_cpu_starting() earlier").

Signed-off-by: Stefan Wiehler 
Reviewed-by: Huacai Chen 
Signed-off-by: Thomas Bogendoerfer

Merge tag 'mips_6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

2023-06-29T22:01:51+00:00

Pull MIPS updates from Thomas Bogendoerfer:

 - add support for TP-Link HC220 G5 v1

 - add support for Wifi/Bluetooth on CI20

 - rework Ralink clock and reset handling

 - cleanups and fixes

* tag 'mips_6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (58 commits)
  MIPS: Loongson64: DTS: Add RTC support to Loongson-2K1000
  MIPS: Loongson64: DTS: Add RTC support to LS7A PCH
  MIPS: OCTEON: octeon-usb: cleanup divider calculation
  MIPS: OCTEON: octeon-usb: introduce dwc3_octeon_{read,write}q
  MIPS: OCTEON: octeon-usb: move gpio config to separate function
  MIPS: OCTEON: octeon-usb: use bitfields for shim register
  MIPS: OCTEON: octeon-usb: use bitfields for host config register
  MIPS: OCTEON: octeon-usb: use bitfields for control register
  MIPS: OCTEON: octeon-usb: add all register offsets
  mips: ralink: match all supported system controller compatible strings
  MIPS: dec: prom: Address -Warray-bounds warning
  MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts
  clk: ralink: mtmips: Fix uninitialized use of ret in mtmips_register_{fixed,factor}_clocks()
  mips: ralink: introduce commonly used remap node function
  mips: pci-mt7620: use dev_info() to log PCIe device detection result
  mips: pci-mt7620: do not print NFTS register value as error log
  MAINTAINERS: add Mediatek MTMIPS Clock maintainer
  mips: ralink: get cpu rate from new driver code
  mips: ralink: remove reset related code
  mips: ralink: mt7620: remove clock related code
  ...

MIPS: Rework smt cmdline parameters

2023-06-09T08:34:14+00:00

Provide a generic smt parameters interface aligned with s390
to allow users to limit smt usage and threads per core.

It replaced previous undocumented "nothreads" parameter for
smp-cps which is ambiguous and does not cover smp-mt.

Signed-off-by: Jiaxun Yang 
Signed-off-by: Thomas Bogendoerfer

MIPS: SMP_CPS: Switch to hotplug core state synchronization

2023-05-15T11:44:58+00:00

Switch to the CPU hotplug core state tracking and synchronization
mechanim. This unfortunately requires to add dead reporting to the non CPS
platforms as CPS is the only user, but it allows an overall consolidation
of this functionality.

No functional change intended.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Michael Kelley 
Tested-by: Oleksandr Natalenko 
Tested-by: Helge Deller  # parisc
Tested-by: Guilherme G. Piccoli  # Steam Deck
Link: https://lore.kernel.org/r/20230512205256.803238859@linutronix.de

MIPS: smp: optimization for flush_tlb_mm when exiting

2022-05-12T15:56:21+00:00

When process exits or execute new binary, it will call function
exit_mmap with old mm, there is such function call trace:
  exit_mmap(struct mm_struct *mm)
      --> tlb_finish_mmu(&tlb, 0, -1)
         --> arch_tlb_finish_mmu(tlb, start, end, force)
	    --> tlb_flush_mmu(tlb);
               --> tlb_flush(struct mmu_gather *tlb)
                  --> flush_tlb_mm(tlb->mm)

It is not necessary to flush tlb since oldmm is not used anymore
by the process, there is similar operations on IA64/ARM64 etc,
this patch adds such optimization on MIPS.

Signed-off-by: Mao Bibo 
Signed-off-by: Thomas Bogendoerfer

MIPS: smp: fill in sibling and core maps earlier

2022-02-16T19:48:10+00:00

After enabling CONFIG_SCHED_CORE (landed during 5.14 cycle),
2-core 2-thread-per-core interAptiv (CPS-driven) started emitting
the following:

[    0.025698] CPU1 revision is: 0001a120 (MIPS interAptiv (multi))
[    0.048183] ------------[ cut here ]------------
[    0.048187] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:6025 sched_core_cpu_starting+0x198/0x240
[    0.048220] Modules linked in:
[    0.048233] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc3+ #35 b7b319f24073fd9a3c2aa7ad15fb7993eec0b26f
[    0.048247] Stack : 817f0000 00000004 327804c8 810eb050 00000000 00000004 00000000 c314fdd1
[    0.048278]         830cbd64 819c0000 81800000 817f0000 83070bf4 00000001 830cbd08 00000000
[    0.048307]         00000000 00000000 815fcbc4 00000000 00000000 00000000 00000000 00000000
[    0.048334]         00000000 00000000 00000000 00000000 817f0000 00000000 00000000 817f6f34
[    0.048361]         817f0000 818a3c00 817f0000 00000004 00000000 00000000 4dc33260 0018c933
[    0.048389]         ...
[    0.048396] Call Trace:
[    0.048399] [<8105a7bc>] show_stack+0x3c/0x140
[    0.048424] [<8131c2a0>] dump_stack_lvl+0x60/0x80
[    0.048440] [<8108b5c0>] __warn+0xc0/0xf4
[    0.048454] [<8108b658>] warn_slowpath_fmt+0x64/0x10c
[    0.048467] [<810bd418>] sched_core_cpu_starting+0x198/0x240
[    0.048483] [<810c6514>] sched_cpu_starting+0x14/0x80
[    0.048497] [<8108c0f8>] cpuhp_invoke_callback_range+0x78/0x140
[    0.048510] [<8108d914>] notify_cpu_starting+0x94/0x140
[    0.048523] [<8106593c>] start_secondary+0xbc/0x280
[    0.048539]
[    0.048543] ---[ end trace 0000000000000000 ]---
[    0.048636] Synchronize counters for CPU 1: done.

...for each but CPU 0/boot.
Basic debug printks right before the mentioned line say:

[    0.048170] CPU: 1, smt_mask:

So smt_mask, which is sibling mask obviously, is empty when entering
the function.
This is critical, as sched_core_cpu_starting() calculates
core-scheduling parameters only once per CPU start, and it's crucial
to have all the parameters filled in at that moment (at least it
uses cpu_smt_mask() which in fact is `&cpu_sibling_map[cpu]` on
MIPS).

A bit of debugging led me to that set_cpu_sibling_map() performing
the actual map calculation, was being invocated after
notify_cpu_start(), and exactly the latter function starts CPU HP
callback round (sched_core_cpu_starting() is basically a CPU HP
callback).
While the flow is same on ARM64 (maps after the notifier, although
before calling set_cpu_online()), x86 started calculating sibling
maps earlier than starting the CPU HP callbacks in Linux 4.14 (see
[0] for the reference). Neither me nor my brief tests couldn't find
any potential caveats in calculating the maps right after performing
delay calibration, but the WARN splat is now gone.
The very same debug prints now yield exactly what I expected from
them:

[    0.048433] CPU: 1, smt_mask: 0-1

[0] https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=76ce7cfe35ef

Signed-off-by: Alexander Lobakin 
Reviewed-by: Philippe Mathieu-Daudé 
Signed-off-by: Thomas Bogendoerfer

sched/core: Initialize the idle task with preemption disabled

2021-05-12T11:01:45+00:00

As pointed out by commit

  de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread")

init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.

As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().

Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().

Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().

Secondary startups were patched via coccinelle:

  @begone@
  @@

  -preempt_disable();
  ...
  cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

Signed-off-by: Valentin Schneider 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com

arch: mips: kernel: Fix two spelling in smp.c

2021-02-03T10:33:48+00:00

s/logcal/logical/
s/intercpu/inter-CPU/

Signed-off-by: Bhaskar Chowdhury 
Acked-by: Randy Dunlap 
Signed-off-by: Thomas Bogendoerfer

smp: Cleanup smp_call_function*()

2020-11-24T15:47:49+00:00

Get rid of the __call_single_node union and cleanup the API a little
to avoid external code relying on the structure layout as much.

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Frederic Weisbecker

Merge tag 'mips_5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

2020-03-31T15:51:45+00:00

Pull MIPS updates from Thomas Bogendoerfer:

 - loongson64 irq rework

 - dmi support loongson

 - replace setup_irq() by request_irq()

 - jazz cleanups

 - minor cleanups and fixes

* tag 'mips_5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (44 commits)
  MIPS: ralink: mt7621: Fix soc_device introduction
  MIPS: Exclude more dsemul code when CONFIG_MIPS_FP_SUPPORT=n
  MIPS/tlbex: Fix LDDIR usage in setup_pw() for Loongson-3
  MIPS: do not compile generic functions for CONFIG_CAVIUM_OCTEON_SOC
  MAINTAINERS: Update Loongson64 entry
  MIPS: Loongson64: Load built-in dtbs
  MIPS: Loongson64: Add generic dts
  dt-bindings: mips: Add loongson boards
  MIPS: Loongson64: Drop legacy IRQ code
  dt-bindings: interrupt-controller: Add Loongson-3 HTPIC
  irqchip: Add driver for Loongson-3 HyperTransport PIC controller
  dt-bindings: interrupt-controller: Add Loongson LIOINTC
  irqchip: loongson-liointc: Workaround LPC IRQ Errata
  irqchip: Add driver for Loongson I/O Local Interrupt Controller
  docs: mips: remove no longer needed au1xxx_ide.rst documentation
  MIPS: Alchemy: remove no longer used au1xxx_ide.h header
  ide: remove no longer used au1xxx-ide driver
  MIPS: Add support for Desktop Management Interface (DMI)
  firmware: dmi: Add macro SMBIOS_ENTRY_POINT_SCAN_START
  MIPS: ralink: mt7621: introduce 'soc_device' initialization
  ...