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Re: [PATCH] seqlock: fix seqlock_write_unlock_impl function
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH] seqlock: fix seqlock_write_unlock_impl function |
Date: |
Thu, 30 Jan 2020 01:27:13 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 29/01/20 15:49, Luc Michel wrote:
> The seqlock write unlock function was incorrectly calling
> seqlock_write_begin() instead of seqlock_write_end(), and was releasing
> the lock before incrementing the sequence. This could lead to a race
> condition and a corrupted sequence number becoming odd even though the
> lock is not held.
>
> Signed-off-by: Luc Michel <address@hidden>
> ---
> include/qemu/seqlock.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/qemu/seqlock.h b/include/qemu/seqlock.h
> index fd408b7ec5..8b6b4ee4bb 100644
> --- a/include/qemu/seqlock.h
> +++ b/include/qemu/seqlock.h
> @@ -53,15 +53,15 @@ static inline void seqlock_write_lock_impl(QemuSeqLock
> *sl, QemuLockable *lock)
> seqlock_write_begin(sl);
> }
> #define seqlock_write_lock(sl, lock) \
> seqlock_write_lock_impl(sl, QEMU_MAKE_LOCKABLE(lock))
>
> -/* Lock out other writers and update the count. */
> +/* Update the count and release the lock. */
> static inline void seqlock_write_unlock_impl(QemuSeqLock *sl, QemuLockable
> *lock)
> {
> + seqlock_write_end(sl);
> qemu_lockable_unlock(lock);
> - seqlock_write_begin(sl);
> }
> #define seqlock_write_unlock(sl, lock) \
> seqlock_write_unlock_impl(sl, QEMU_MAKE_LOCKABLE(lock))
>
>
>
Queued, thanks very much.
Paolo