diff options
| author | Rik van Riel <riel@surriel.com> | 2024-07-15 13:49:41 -0400 |
|---|---|---|
| committer | Neeraj Upadhyay <neeraj.upadhyay@kernel.org> | 2024-08-15 00:06:48 +0530 |
| commit | 9fbaa44114ca6b69074a488295e86a9fa7e685f9 (patch) | |
| tree | 18da76d874fe7db6bbe10cf3100f2d3ee3e9f58c /kernel/smp.c | |
| parent | d40760d6811d55172ba6b90ebd2a60a75f88bffe (diff) | |
smp: print only local CPU info when sched_clock goes backward
About 40% of all csd_lock warnings observed in our fleet appear to
be due to sched_clock() going backward in time (usually only a little
bit), resulting in ts0 being larger than ts2.
When the local CPU is at fault, we should print out a message reflecting
that, rather than trying to get the remote CPU's stack trace.
Signed-off-by: Rik van Riel <riel@surriel.com>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Diffstat (limited to 'kernel/smp.c')
| -rw-r--r-- | kernel/smp.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index b484ee6dcaf6..f25e20617b7e 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -254,6 +254,14 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in csd_lock_timeout_ns == 0)) return false; + if (ts0 > ts2) { + /* Our own sched_clock went backward; don't blame another CPU. */ + ts_delta = ts0 - ts2; + pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta); + *ts1 = ts2; + return false; + } + firsttime = !*bug_id; if (firsttime) *bug_id = atomic_inc_return(&csd_bug_count); |