Messages in this thread | | | Date | Tue, 19 Apr 2022 09:11:46 +0200 | Subject | Re: [PATCH rcu 04/11] kernel/smp: Provide boot-time timeout for CSD lock diagnostics | From | Juergen Gross <> |
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On 19.04.22 00:53, Paul E. McKenney wrote: > Debugging of problems involving insanely long-running SMI handlers > proceeds better if the CSD-lock timeout can be adjusted. This commit > therefore provides a new smp.csd_lock_timeout kernel boot parameter > that specifies the timeout in milliseconds. The default remains at the > previously hard-coded value of five seconds. > > Cc: Rik van Riel <riel@surriel.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Cc: Juergen Gross <jgross@suse.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > --- > Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++ > kernel/smp.c | 7 +++++-- > 2 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 3f1cc5e317ed..645c4c001b16 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -5377,6 +5377,17 @@ > smart2= [HW] > Format: <io1>[,<io2>[,...,<io8>]] > > + smp.csd_lock_timeout= [KNL] > + Specify the period of time in milliseconds > + that smp_call_function() and friends will wait > + for a CPU to release the CSD lock. This is > + useful when diagnosing bugs involving CPUs > + disabling interrupts for extended periods > + of time. Defaults to 5,000 milliseconds, and > + setting a value of zero disables this feature. > + This feature may be more efficiently disabled > + using the csdlock_debug- kernel parameter. > + > smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices > smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port > smsc-ircc2.ircc_sir= [HW] SIR base I/O port > diff --git a/kernel/smp.c b/kernel/smp.c > index 01a7c1706a58..d82439bac401 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -183,7 +183,9 @@ static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); > static DEFINE_PER_CPU(void *, cur_csd_info); > static DEFINE_PER_CPU(struct cfd_seq_local, cfd_seq_local); > > -#define CSD_LOCK_TIMEOUT (5ULL * NSEC_PER_SEC) > +static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ > +module_param(csd_lock_timeout, ulong, 0444); > + > static atomic_t csd_bug_count = ATOMIC_INIT(0); > static u64 cfd_seq; > > @@ -329,6 +331,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * > u64 ts2, ts_delta; > call_single_data_t *cpu_cur_csd; > unsigned int flags = READ_ONCE(csd->node.u_flags); > + unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; > > if (!(flags & CSD_FLAG_LOCK)) { > if (!unlikely(*bug_id)) > @@ -341,7 +344,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * > > ts2 = sched_clock(); > ts_delta = ts2 - *ts1; > - if (likely(ts_delta <= CSD_LOCK_TIMEOUT)) > + if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns <= 0))
csd_lock_timeout_ns is unsigned, so "csd_lock_timeout_ns <= 0" should be rather "csd_lock_timeout_ns == 0".
With that fixed you can add my
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |