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kernel/smp: Provide boot-time timeout for CSD lock diagnostics

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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.

[ paulmck: Apply feedback from Juergen Gross. ]

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>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-02-28 18:08:33 -08:00
parent c708b08c65
commit 3791a22374
2 changed files with 16 additions and 2 deletions
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11
Documentation/admin-guide/kernel-parameters.txt
View file

@ -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

7
kernel/smp.c
View file

@ -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))
return false;
firsttime = !*bug_id;