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| author |   Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2025-04-16 18:29:08 +0200 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2025-05-03 12:02:06 +0200 |
| commit | 3f6b233018af2a6fb449faa324d94a437e2e47ce (patch) | |
| tree | 91387ca8fecbc371c18b3f3aeb9cbafe5c48212e /kernel/futex/waitwake.c | |
| parent | futex: Create private_hash() get/put class (diff) | |
| download | wireguard-linux-3f6b233018af2a6fb449faa324d94a437e2e47ce.tar.xz wireguard-linux-3f6b233018af2a6fb449faa324d94a437e2e47ce.zip | |
futex: Acquire a hash reference in futex_wait_multiple_setup()
futex_wait_multiple_setup() changes task_struct::__state to
!TASK_RUNNING and then enqueues on multiple futexes. Every
futex_q_lock() acquires a reference on the global hash which is
dropped later.
If a rehash is in progress then the loop will block on
mm_struct::futex_hash_bucket for the rehash to complete and this will
lose the previously set task_struct::__state.
Acquire a reference on the local hash to avoiding blocking on
mm_struct::futex_hash_bucket.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250416162921.513656-9-bigeasy@linutronix.de
Diffstat (limited to '')
| -rw-r--r-- | kernel/futex/waitwake.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c index d52541bcc07e..bd8fef0f8d18 100644 --- a/kernel/futex/waitwake.c +++ b/kernel/futex/waitwake.c @@ -407,6 +407,12 @@ int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *woken) u32 uval; /* + * Make sure to have a reference on the private_hash such that we + * don't block on rehash after changing the task state below. + */ + guard(private_hash)(); + + /* * Enqueuing multiple futexes is tricky, because we need to enqueue * each futex on the list before dealing with the next one to avoid * deadlocking on the hash bucket. But, before enqueuing, we need to |