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x86/alternatives: Document the text_poke_bp_batch() synchronization rules a bit more

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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250411054105.2341982-3-mingo@kernel.org
This commit is contained in:
Peter Zijlstra
2025-04-11 11:01:33 +02:00
committed by Ingo Molnar
parent 4334336e76
commit d60e4b2410
1 changed files with 7 additions and 0 deletions
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arch/x86/kernel/alternative.c
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@@ -2751,6 +2751,13 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
/*
* Remove and wait for refs to be zero.
*
* Notably, if after step-3 above the INT3 got removed, then the
* text_poke_sync() will have serialized against any running INT3
* handlers and the below spin-wait will not happen.
*
* IOW. unless the replacement instruction is INT3, this case goes
* unused.
*/
for_each_possible_cpu(i) {
atomic_t *refs = per_cpu_ptr(&bp_refs, i);