From: Waiman Long <longman@redhat.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH] locking/rwsem: Add up_write_non_owner() for percpu_up_write()
Date: Wed, 4 Apr 2018 10:40:09 -0400 [thread overview]
Message-ID: <7745dbe3-f9c0-d624-e692-0d4320c0627a@redhat.com> (raw)
In-Reply-To: <1522852646-2196-1-git-send-email-longman@redhat.com>
On 04/04/2018 10:37 AM, Waiman Long wrote:
> The commit 8c5db92a705d ("locking/rwsem: Add DEBUG_RWSEMS to look for
> lock/unlock mismatches") causes a warning in ext4 fstests due to the
> fact that the freeze and thaw ioctls, by design, are run in different
> processes. This is not a bug in the commit itself. Rather, we need a
> up_write() variant that annotates the fact that it can be called from
> a task different from the one that took the lock.
>
> The new API is up_write_non_owner() and the percpu_up_write() function
> is modified to use it instead of the plain up_write().
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> include/linux/rwsem.h | 6 ++++++
> kernel/locking/percpu-rwsem.c | 4 +++-
> kernel/locking/rwsem.c | 13 +++++++++++++
> 3 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
> index 56707d5..0e2a425 100644
> --- a/include/linux/rwsem.h
> +++ b/include/linux/rwsem.h
> @@ -187,4 +187,10 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem)
> # define up_read_non_owner(sem) up_read(sem)
> #endif
>
> +#ifdef CONFIG_DEBUG_RWSEMS
> +extern void up_write_non_owner(struct rw_semaphore *sem);
> +#else
> +# define up_write_non_owner(sem) up_write(sem)
> +#endif
> +
> #endif /* _LINUX_RWSEM_H */
> diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
> index 883cf1b..13decf2 100644
> --- a/kernel/locking/percpu-rwsem.c
> +++ b/kernel/locking/percpu-rwsem.c
> @@ -179,8 +179,10 @@ void percpu_up_write(struct percpu_rw_semaphore *sem)
>
> /*
> * Release the write lock, this will allow readers back in the game.
> + * percpu_up_write() may be called from a task different from the one
> + * taking the lock.
> */
> - up_write(&sem->rw_sem);
> + up_write_non_owner(&sem->rw_sem);
>
> /*
> * Once this completes (at least one RCU-sched grace period hence) the
> diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
> index 30465a2..140d5ef 100644
> --- a/kernel/locking/rwsem.c
> +++ b/kernel/locking/rwsem.c
> @@ -222,4 +222,17 @@ void up_read_non_owner(struct rw_semaphore *sem)
>
> #endif
>
> +#ifdef CONFIG_DEBUG_RWSEMS
> +/*
> + * release a write lock from a different task
> + */
> +void up_write_non_owner(struct rw_semaphore *sem)
> +{
> + rwsem_release(&sem->dep_map, 1, _RET_IP_);
> + DEBUG_RWSEMS_WARN_ON(!sem->owner || (sem->owner == RWSEM_READER_OWNED));
>
> + rwsem_clear_owner(sem);
> + __up_write(sem);
> +}
> +EXPORT_SYMBOL(up_write_non_owner);
> +#endif
Theodore,
Could you try this patch to see if it can fix your fstests warning?
Thanks,
Longman
next prev parent reply other threads:[~2018-04-04 14:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-04 14:37 [PATCH] locking/rwsem: Add up_write_non_owner() for percpu_up_write() Waiman Long
2018-04-04 14:40 ` Waiman Long [this message]
2018-04-05 3:14 ` Theodore Y. Ts'o
2018-04-09 11:20 ` Oleg Nesterov
2018-04-09 13:32 ` Waiman Long
2018-04-09 14:22 ` Oleg Nesterov
2018-05-14 19:36 ` Waiman Long
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7745dbe3-f9c0-d624-e692-0d4320c0627a@redhat.com \
--to=longman@redhat.com \
--cc=dave@stgolabs.net \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).