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smp: Disable preemption explicitly in __csd_lock_wait()

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The CSD lock wait debugging code in __csd_lock_wait() must run with
preemption disabled. The smp function call mechanisms which invoke it
currently keep preemption disabled across the wait, so the debugging code
inherits that guarantee from its callers.

Keeping preemption disabled across the whole smp function call operation
can induce large scheduling latencies. Shortening the caller-side
preemption-disabled region would invoke __csd_lock_wait() with preemption
enabled.

Prepare for that by disabling preemption explicitly around the CSD lock
wait debugging code in __csd_lock_wait().

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Muchun Song <muchun.song@linux.dev>
Link: https://patch.msgid.link/20260709122933.4021501-2-zhouchuyi@bytedance.com
This commit is contained in:
Chuyi Zhou
2026-07-16 09:24:55 +02:00
committed by Thomas Gleixner
parent aeec9d9ae6
commit b46883305f
1 changed files with 2 additions and 0 deletions
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kernel/smp.c
+2
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@@ -335,6 +335,8 @@ static void __csd_lock_wait(call_single_data_t *csd)
int bug_id = 0;
u64 ts0, ts1;
guard(preempt)();
ts1 = ts0 = ktime_get_mono_fast_ns();
for (;;) {
if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages))