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
*
* 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
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();
return sched_clock_cpu(cpu);
}
+extern u64 local_clock_noinstr(void);
extern u64 local_clock(void);
#endif
s64 delta;
again:
- now = sched_clock();
+ now = sched_clock_noinstr();
delta = now - scd->tick_raw;
if (unlikely(delta < 0))
delta = 0;
return clock;
}
-noinstr u64 local_clock(void)
+noinstr u64 local_clock_noinstr(void)
{
u64 clock;
if (static_branch_likely(&__sched_clock_stable))
- return sched_clock() + __sched_clock_offset;
+ return sched_clock_noinstr() + __sched_clock_offset;
if (!static_branch_likely(&sched_clock_running))
- return sched_clock();
+ return sched_clock_noinstr();
- preempt_disable_notrace();
clock = sched_clock_local(this_scd());
- preempt_enable_notrace();
return clock;
}
+
+u64 local_clock(void)
+{
+ u64 now;
+ preempt_disable_notrace();
+ now = local_clock_noinstr();
+ preempt_enable_notrace();
+ return now;
+}
EXPORT_SYMBOL_GPL(local_clock);
static notrace u64 sched_clock_remote(struct sched_clock_data *scd)