Messages in this thread Patch in this message | | | Date | Tue, 1 Mar 2022 11:34:45 -0800 | From | "Paul E. McKenney" <> | Subject | [PATCH RFC 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.
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>
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2ac18d36805cf..6e38727af2552 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5333,6 +5333,17 @@ 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 01a7c1706a58b..d82439bac4016 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)) return false; firsttime = !*bug_id;
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