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CSD lock commits for v6.7

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This series adds a kernel boot parameter that causes the kernel to
 panic if one of the call_smp_function() APIs is stalled for more than
 the specified duration.  This is useful in deployments in which a clean
 panic is preferable to an indefinite stall.
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Merge tag 'csd-lock.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull CSD lock update from Paul McKenney:
 "This adds a kernel boot parameter that causes the kernel to panic if
  one of the call_smp_function() APIs is stalled for more than the
  specified duration.

  This is useful in deployments in which a clean panic is preferable to
  an indefinite stall"

* tag 'csd-lock.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  smp,csd: Throw an error if a CSD lock is stuck for too long
This commit is contained in:
Linus Torvalds 2023-10-30 17:56:53 -10:00
commit 9a0f53e0cf
2 changed files with 19 additions and 1 deletions
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7
Documentation/admin-guide/kernel-parameters.txt
View File

@ -5864,6 +5864,13 @@
This feature may be more efficiently disabled
using the csdlock_debug- kernel parameter.
smp.panic_on_ipistall= [KNL]
If a csd_lock_timeout extends for more than
the specified number of milliseconds, panic the
system. By default, let CSD-lock acquisition
take as long as they take. Specifying 300,000
for this value provides a 5-minute timeout.
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

13
kernel/smp.c
View File

@ -170,6 +170,8 @@ static DEFINE_PER_CPU(void *, cur_csd_info);
static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */
module_param(csd_lock_timeout, ulong, 0444);
static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */
module_param(panic_on_ipistall, int, 0444);
static atomic_t csd_bug_count = ATOMIC_INIT(0);
@ -230,6 +232,7 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in
}
ts2 = sched_clock();
/* How long since we last checked for a stuck CSD lock.*/
ts_delta = ts2 - *ts1;
if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0))
return false;
@ -243,9 +246,17 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in
else
cpux = cpu;
cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
/* How long since this CSD lock was stuck. */
ts_delta = ts2 - ts0;
pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",
firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0,
firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta,
cpu, csd->func, csd->info);
/*
* If the CSD lock is still stuck after 5 minutes, it is unlikely
* to become unstuck. Use a signed comparison to avoid triggering
* on underflows when the TSC is out of sync between sockets.
*/
BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC));
if (cpu_cur_csd && csd != cpu_cur_csd) {
pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
*bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),