Messages in this thread | | | Date | Fri, 6 Oct 2023 20:48:23 +0200 | Subject | Re: [PATCH smp,csd] Throw an error if a CSD lock is stuck for too long | From | Jonas Oberhauser <> |
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Is this related to the qspinlock issue you described earlier?
jonas
Am 10/5/2023 um 6:48 PM schrieb Paul E. McKenney: > The CSD lock seems to get stuck in 2 "modes". When it gets stuck > temporarily, it usually gets released in a few seconds, and sometimes > up to one or two minutes. > > If the CSD lock stays stuck for more than several minutes, it never > seems to get unstuck, and gradually more and more things in the system > end up also getting stuck. > > In the latter case, we should just give up, so the system can dump out > a little more information about what went wrong, and, with panic_on_oops > and a kdump kernel loaded, dump a whole bunch more information about > what might have gone wrong. > > Question: should this have its own panic_on_ipistall switch in > /proc/sys/kernel, or maybe piggyback on panic_on_oops in a different > way than via BUG_ON? > > Signed-off-by: Rik van Riel <riel@surriel.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > diff --git a/kernel/smp.c b/kernel/smp.c > index 8455a53465af..059f1f53fc6b 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -230,6 +230,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * > } > > ts2 = sched_clock(); > + /* How long since we last checked for a stuck CSD lock.*/ > ts_delta = ts2 - *ts1; > if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0)) > return false; > @@ -243,9 +244,17 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * > else > cpux = cpu; > cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ > + /* How long since this CSD lock was stuck. */ > + ts_delta = ts2 - ts0; > pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n", > - firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0, > + firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta, > cpu, csd->func, csd->info); > + /* > + * If the CSD lock is still stuck after 5 minutes, it is unlikely > + * to become unstuck. Use a signed comparison to avoid triggering > + * on underflows when the TSC is out of sync between sockets. > + */ > + BUG_ON((s64)ts_delta > 300000000000LL); > if (cpu_cur_csd && csd != cpu_cur_csd) { > pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", > *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
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