Re: [PATCH] kcsan, seqlock: Support seqcount_latch_t
From: Peter Zijlstra
Date: Thu Oct 31 2024 - 05:20:56 EST
On Wed, Oct 30, 2024 at 09:48:15PM +0100, Peter Zijlstra wrote:
> diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
> index 68d6c1190ac7..4958b40ba6c9 100644
> --- a/kernel/time/sched_clock.c
> +++ b/kernel/time/sched_clock.c
> @@ -102,7 +102,9 @@ unsigned long long notrace sched_clock(void)
> {
> unsigned long long ns;
> preempt_disable_notrace();
> + kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);
> ns = sched_clock_noinstr();
> + kcsan_atomic_next(0);
> preempt_enable_notrace();
> return ns;
> }
You might want to consider also folding something like this in.
That should give this instrumented version instrumentation :-)
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index 68d6c1190ac7..db26f343233f 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -80,7 +80,7 @@ notrace int sched_clock_read_retry(unsigned int seq)
return raw_read_seqcount_latch_retry(&cd.seq, seq);
}
-unsigned long long noinstr sched_clock_noinstr(void)
+static __always_inline unsigned long long __sched_clock(void)
{
struct clock_read_data *rd;
unsigned int seq;
@@ -98,11 +98,16 @@ unsigned long long noinstr sched_clock_noinstr(void)
return res;
}
+unsigned long long noinstr sched_clock_noinstr(void)
+{
+ return __sched_clock();
+}
+
unsigned long long notrace sched_clock(void)
{
unsigned long long ns;
preempt_disable_notrace();
- ns = sched_clock_noinstr();
+ ns = __sched_clock();
preempt_enable_notrace();
return ns;
}