Commit 311e062a authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'csd-lock.2024.11.16a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu 

Pull CSD-lock update from Paul McKenney:
 "This switches from sched_clock() to ktime_get_mono_fast_ns(), which on
  x86 switches from the rdtsc instruction to the rdtscp instruction,
  thus avoiding instruction reorderings that cause false-positive
  reports of CSD-lock stalls of almost 2^46 nanoseconds. These false
  positives are rare, but really are seen in the wild"

* tag 'csd-lock.2024.11.16a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  locking/csd-lock: Switch from sched_clock() to ktime_get_mono_fast_ns()
parents d7d4102f 9861f7f6

kernel/smp.c

+2 −2
Original line number Diff line number Diff line
@@ -246,7 +246,7 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in 
		return true;

	}



	ts2 = sched_clock();

	ts2 = ktime_get_mono_fast_ns();

	/* How long since we last checked for a stuck CSD lock.*/

	ts_delta = ts2 - *ts1;

	if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) *
@@ -321,7 +321,7 @@ static void __csd_lock_wait(call_single_data_t *csd) 
	int bug_id = 0;

	u64 ts0, ts1;



	ts1 = ts0 = sched_clock();

	ts1 = ts0 = ktime_get_mono_fast_ns();

	for (;;) {

		if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages))

			break;