diff options
| author |   Marco Elver <elver@google.com> | 2024-11-04 16:43:06 +0100 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2024-11-05 12:55:35 +0100 |
| commit | 8ab40fc2b9086b915e46890bb9252dc7692f1da0 (patch) | |
| tree | 8e682c5a7b473c8f54e5b313c5c237db0f875957 | |
| parent | time/sched_clock: Swap update_clock_read_data() latch writes (diff) | |
| download | wireguard-linux-8ab40fc2b9086b915e46890bb9252dc7692f1da0.tar.xz wireguard-linux-8ab40fc2b9086b915e46890bb9252dc7692f1da0.zip | |
time/sched_clock: Broaden sched_clock()'s instrumentation coverage
Most of sched_clock()'s implementation is ineligible for instrumentation
due to relying on sched_clock_noinstr().
Split the implementation off into an __always_inline function
__sched_clock(), which is then used by the noinstr and instrumentable
version, to allow more of sched_clock() to be covered by various
instrumentation.
This will allow instrumentation with the various sanitizers (KASAN,
KCSAN, KMSAN, UBSAN). For KCSAN, we know that raw seqcount_latch usage
without annotations will result in false positive reports: tell it that
all of __sched_clock() is "atomic" for the latch reader; later changes
in this series will take care of the writers.
Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-3-elver@google.com
| -rw-r--r-- | kernel/time/sched_clock.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index 85595fcf6aa2..29bdf309dae8 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 +98,23 @@ 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(); + /* + * All of __sched_clock() is a seqcount_latch reader critical section, + * but relies on the raw helpers which are uninstrumented. For KCSAN, + * mark all accesses in __sched_clock() as atomic. + */ + kcsan_nestable_atomic_begin(); + ns = __sched_clock(); + kcsan_nestable_atomic_end(); preempt_enable_notrace(); return ns; } |