linux.git/arch/arm/kernel/smp.c, branch v6.5

ARM: smp: Switch to hotplug core state synchronization

2023-05-15T11:44:57+00:00

Switch to the CPU hotplug core state tracking and synchronization
mechanim. 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/20230512205256.635326070@linutronix.de

Merge tag 'smp-core-2023-04-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-04-28T22:03:43+00:00

Pull SMP cross-CPU function-call updates from Ingo Molnar:

 - Remove diagnostics and adjust config for CSD lock diagnostics

 - Add a generic IPI-sending tracepoint, as currently there's no easy
   way to instrument IPI origins: it's arch dependent and for some major
   architectures it's not even consistently available.

* tag 'smp-core-2023-04-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  trace,smp: Trace all smp_function_call*() invocations
  trace: Add trace_ipi_send_cpu()
  sched, smp: Trace smp callback causing an IPI
  smp: reword smp call IPI comment
  treewide: Trace IPIs sent via smp_send_reschedule()
  irq_work: Trace self-IPIs sent via arch_irq_work_raise()
  smp: Trace IPIs sent via arch_send_call_function_ipi_mask()
  sched, smp: Trace IPIs sent via send_call_function_single_ipi()
  trace: Add trace_ipi_send_cpumask()
  kernel/smp: Make csdlock_debug= resettable
  locking/csd_lock: Remove per-CPU data indirection from CSD lock debugging
  locking/csd_lock: Remove added data from CSD lock debugging
  locking/csd_lock: Add Kconfig option for csd_debug default

cpu: Mark panic_smp_self_stop() __noreturn

2023-04-14T15:31:25+00:00

In preparation for improving objtool's handling of weak noreturn
functions, mark panic_smp_self_stop() __noreturn.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/92d76ab5c8bf660f04fdcd3da1084519212de248.1681342859.git.jpoimboe@kernel.org

treewide: Trace IPIs sent via smp_send_reschedule()

2023-03-24T10:01:28+00:00

To be able to trace invocations of smp_send_reschedule(), rename the
arch-specific definitions of it to arch_smp_send_reschedule() and wrap it
into an smp_send_reschedule() that contains a tracepoint.

Changes to include the declaration of the tracepoint were driven by the
following coccinelle script:

  @func_use@
  @@
  smp_send_reschedule(...);

  @include@
  @@
  #include 

  @no_include depends on func_use && !include@
  @@
    #include <...>
  +
  + #include 

[csky bits]
[riscv bits]
Signed-off-by: Valentin Schneider 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Guo Ren 
Acked-by: Palmer Dabbelt 
Link: https://lore.kernel.org/r/20230307143558.294354-6-vschneid@redhat.com

sched, smp: Trace IPIs sent via send_call_function_single_ipi()

2023-03-24T10:01:27+00:00

send_call_function_single_ipi() is the thing that sends IPIs at the bottom
of smp_call_function*() via either generic_exec_single() or
smp_call_function_many_cond(). Give it an IPI-related tracepoint.

Note that this ends up tracing any IPI sent via __smp_call_single_queue(),
which covers __ttwu_queue_wakelist() and irq_work_queue_on() "for free".

Signed-off-by: Valentin Schneider 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Steven Rostedt (Google) 
Acked-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20230307143558.294354-3-vschneid@redhat.com

sched/idle: Mark arch_cpu_idle_dead() __noreturn

2023-03-08T16:44:28+00:00

Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
return"), in Xen, when a previously offlined CPU was brought back
online, it unexpectedly resumed execution where it left off in the
middle of the idle loop.

There were some hacks to make that work, but the behavior was surprising
as do_idle() doesn't expect an offlined CPU to return from the dead (in
arch_cpu_idle_dead()).

Now that Xen has been fixed, and the arch-specific implementations of
arch_cpu_idle_dead() also don't return, give it a __noreturn attribute.

This will cause the compiler to complain if an arch-specific
implementation might return.  It also improves code generation for both
caller and callee.

Also fixes the following warning:

  vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction

Reported-by: Paul E. McKenney 
Tested-by: Paul E. McKenney 
Link: https://lore.kernel.org/r/60d527353da8c99d4cf13b6473131d46719ed16d.1676358308.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf

arm/cpu: Add unreachable() to arch_cpu_idle_dead()

2023-03-06T23:34:04+00:00

arch_cpu_idle_dead() doesn't return.  Make that visible to the compiler
with an unreachable() code annotation.

Link: https://lkml.kernel.org/r/20230216183851.s5bnvniomq44rytu@treble
Signed-off-by: Josh Poimboeuf

arm, smp: Remove trace_.*_rcuidle() usage

2023-01-13T10:48:15+00:00

None of these functions should ever be ran with RCU disabled anymore.

Specifically, do_handle_IPI() is only called from handle_IPI() which
explicitly does irq_enter()/irq_exit() which ensures RCU is watching.

The problem with smp_cross_call() was, per commit description:

   7c64cc0531fa ("arm: Use _rcuidle for smp_cross_call() tracepoints")

... that cpuidle_enter_state_coupled() already had RCU disabled, but that's
long been fixed by commit:

  1098582a0f6c ("sched,idle,rcu: Push rcu_idle deeper into the idle path")

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Tested-by: Tony Lindgren 
Tested-by: Ulf Hansson 
Reviewed-by: Ulf Hansson 
Acked-by: Rafael J. Wysocki 
Acked-by: Frederic Weisbecker 
Link: https://lore.kernel.org/r/20230112195540.743432118@infradead.org

ARM: 9257/1: Disable FIQs (but not IRQs) on CPUs shutdown paths

2022-11-07T14:19:02+00:00

Currently the regular CPU shutdown path for ARM disables IRQs/FIQs
in the secondary CPUs - smp_send_stop() calls ipi_cpu_stop(), which
is responsible for that. IRQs are architecturally masked when we
take an interrupt, but FIQs are high priority than IRQs, hence they
aren't masked. With that said, it makes sense to disable FIQs here,
but there's no need for (re-)disabling IRQs.

More than that: there is an alternative path for disabling CPUs,
in the form of function crash_smp_send_stop(), which is used for
kexec/panic path. This function relies on a SMP call that also
triggers a busy-wait loop [at machine_crash_nonpanic_core()], but
without disabling FIQs. This might lead to odd scenarios, like
early interrupts in the boot of kexec'd kernel or even interrupts
in secondary "disabled" CPUs while the main one still works in the
panic path and assumes all secondary CPUs are (really!) off.

So, let's disable FIQs in both paths and *not* disable IRQs a second
time, since they are already masked in both paths by the architecture.
This way, we keep both CPU quiesce paths consistent and safe.

Cc: Marc Zyngier 
Cc: Michael Kelley 
Signed-off-by: Guilherme G. Piccoli 
Signed-off-by: Russell King (Oracle)

profile: setup_profiling_timer() is moslty not implemented

2022-07-30T01:12:36+00:00

The setup_profiling_timer() is mostly un-implemented by many
architectures.  In many places it isn't guarded by CONFIG_PROFILE which is
needed for it to be used.  Make it a weak symbol in kernel/profile.c and
remove the 'return -EINVAL' implementations from the kenrel.

There are a couple of architectures which do return 0 from the
setup_profiling_timer() function but they don't seem to do anything else
with it.  To keep the /proc compatibility for now, leave these for a
future update or removal.

On ARM, this fixes the following sparse warning:
arch/arm/kernel/smp.c:793:5: warning: symbol 'setup_profiling_timer' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220721195509.418205-1-ben-linux@fluff.org
Signed-off-by: Ben Dooks 
Signed-off-by: Andrew Morton