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sched/clock: Provide local_clock_noinstr()

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Now that all ARCH_WANTS_NO_INSTR architectures (arm64, loongarch,
s390, x86) provide sched_clock_noinstr(), use this to provide
local_clock_noinstr().

This local_clock_noinstr() will be safe to use from noinstr code with
the assumption that any such noinstr code is non-preemptible (it had
better be, entry code will have IRQs disabled while __cpuidle must
have preemption disabled).

Specifically, preempt_enable_notrace(), a common part of many a
sched_clock() implementation calls out to schedule() -- even though,
per the above, it will never trigger -- which frustrates noinstr
validation.

  vmlinux.o: warning: objtool: local_clock+0xb5: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.978624636@infradead.org
This commit is contained in:
Peter Zijlstra
2023-05-19 12:21:10 +02:00
parent 5c5e9a2b25
commit fb7d4948c4
2 changed files with 29 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/sched/clock.h
View File

@@ -12,7 +12,16 @@
*
* Please use one of the three interfaces below.
*/
extern unsigned long long notrace sched_clock(void);
extern u64 sched_clock(void);
#if defined(CONFIG_ARCH_WANTS_NO_INSTR) || defined(CONFIG_GENERIC_SCHED_CLOCK)
extern u64 sched_clock_noinstr(void);
#else
static __always_inline u64 sched_clock_noinstr(void)
{
return sched_clock();
}
#endif
/*
* See the comment in kernel/sched/clock.c
@@ -45,6 +54,11 @@ static inline u64 cpu_clock(int cpu)
return sched_clock();
}
static __always_inline u64 local_clock_noinstr(void)
{
return sched_clock_noinstr();
}
static __always_inline u64 local_clock(void)
{
return sched_clock();
@@ -79,6 +93,7 @@ static inline u64 cpu_clock(int cpu)
return sched_clock_cpu(cpu);
}
extern u64 local_clock_noinstr(void);
extern u64 local_clock(void);
#endif