Commit 3791a223 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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



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: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent c708b08c

Documentation/admin-guide/kernel-parameters.txt

+11 −0
Original line number Diff line number Diff line
@@ -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

kernel/smp.c

+5 −2
Original line number Diff line number Diff line
@@ -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;