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| author | Thomas Gleixner <tglx@linutronix.de> | 2019-11-06 22:55:45 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-01-30 13:32:12 +0100 |
| commit | 7f237695d3f02730d2dd60c83e92abe1487c7e89 (patch) | |
| tree | 44f8df7ce18b2a3332a4469f696f553bbe5830fd /kernel/futex.c | |
| parent | f9b0c6c556dbf3694fee05f1334830ce2ec1f5bc (diff) | |
| download | linux-stable-7f237695d3f02730d2dd60c83e92abe1487c7e89.tar.gz linux-stable-7f237695d3f02730d2dd60c83e92abe1487c7e89.tar.bz2 linux-stable-7f237695d3f02730d2dd60c83e92abe1487c7e89.zip | |
futex: Provide distinct return value when owner is exiting
commit ac31c7ff8624409ba3c4901df9237a616c187a5d upstream
attach_to_pi_owner() returns -EAGAIN for various cases:
- Owner task is exiting
- Futex value has changed
The caller drops the held locks (hash bucket, mmap_sem) and retries the
operation. In case of the owner task exiting this can result in a live
lock.
As a preparatory step for seperating those cases, provide a distinct return
value (EBUSY) for the owner exiting case.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.935606117@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 1b279ac3e969..0ad73e053be7 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1182,11 +1182,11 @@ static int handle_exit_race(u32 __user *uaddr, u32 uval, u32 uval2; /* - * If the futex exit state is not yet FUTEX_STATE_DEAD, wait - * for it to finish. + * If the futex exit state is not yet FUTEX_STATE_DEAD, tell the + * caller that the alleged owner is busy. */ if (tsk && tsk->futex_state != FUTEX_STATE_DEAD) - return -EAGAIN; + return -EBUSY; /* * Reread the user space value to handle the following situation: @@ -2095,12 +2095,13 @@ retry_private: if (!ret) goto retry; goto out; + case -EBUSY: case -EAGAIN: /* * Two reasons for this: - * - Owner is exiting and we just wait for the + * - EBUSY: Owner is exiting and we just wait for the * exit to complete. - * - The user space value changed. + * - EAGAIN: The user space value changed. */ double_unlock_hb(hb1, hb2); hb_waiters_dec(hb2); @@ -2873,12 +2874,13 @@ retry_private: goto out_unlock_put_key; case -EFAULT: goto uaddr_faulted; + case -EBUSY: case -EAGAIN: /* * Two reasons for this: - * - Task is exiting and we just wait for the + * - EBUSY: Task is exiting and we just wait for the * exit to complete. - * - The user space value changed. + * - EAGAIN: The user space value changed. */ queue_unlock(hb); put_futex_key(&q.key); |