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authorLinus Torvalds <torvalds@linux-foundation.org>2023-10-30 17:56:53 -1000
committerLinus Torvalds <torvalds@linux-foundation.org>2023-10-30 17:56:53 -1000
commit9a0f53e0cfc2ef262c05b8e4ab89e7f2accaf96c (patch)
treed5d05ad14bb222c7d20f96e5738eb8ff95a797a3 /kernel
parent6750f0de53b7d64a4deffa62944ea431a153ec48 (diff)
parent94b3f0b5af2c7af69e3d6e0cdd9b0ea535f22186 (diff)
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/smp.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index 8c714583786b..f085ebcdf9e7 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -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)),