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@xxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- 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@xxxxxxxx> Juergen
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