From: Joel Fernandes <joel@joelfernandes.org>
To: "Connor O'Brien" <connoro@google.com>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com,
John Stultz <jstultz@google.com>,
Joel Fernandes <joelaf@google.com>,
Qais Yousef <qais.yousef@arm.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [RFC PATCH 04/11] locking/mutex: make mutex::wait_lock irq safe
Date: Thu, 13 Oct 2022 00:30:02 -0400 [thread overview]
Message-ID: <CAEXW_YRSj3T7MY1qu=hy7+Wf=p34bBKnCLfE7vMJUmFbg0wCKA@mail.gmail.com> (raw)
In-Reply-To: <20221003214501.2050087-5-connoro@google.com>
On Mon, Oct 3, 2022 at 5:45 PM Connor O'Brien <connoro@google.com> wrote:
>
> From: Juri Lelli <juri.lelli@redhat.com>
>
> mutex::wait_lock might be nested under rq->lock.
>
> Make it irq safe then.
Hi Juri, can you give an example where not doing this is an issue?
When nested under rq->lock, interrupts should already be disabled,
otherwise try_to_wake_up() from an interrupt can cause a deadlock no?
Then, why do you need this patch?
Thanks.
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lkml.kernel.org/r/20181009092434.26221-7-juri.lelli@redhat.com
> [rebase & fix {un,}lock_wait_lock helpers in ww_mutex.h]
> Signed-off-by: Connor O'Brien <connoro@google.com>
> ---
> kernel/locking/mutex.c | 18 ++++++++++--------
> kernel/locking/ww_mutex.h | 22 ++++++++++++----------
> 2 files changed, 22 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 7800380219db..f39e9ee3c4d0 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -572,6 +572,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> {
> struct mutex_waiter waiter;
> struct ww_mutex *ww;
> + unsigned long flags;
> int ret;
>
> if (!use_ww_ctx)
> @@ -614,7 +615,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> return 0;
> }
>
> - raw_spin_lock(&lock->wait_lock);
> + raw_spin_lock_irqsave(&lock->wait_lock, flags);
> /*
> * After waiting to acquire the wait_lock, try again.
> */
> @@ -676,7 +677,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> goto err;
> }
>
> - raw_spin_unlock(&lock->wait_lock);
> + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
> if (ww_ctx)
> ww_ctx_wake(ww_ctx);
> schedule_preempt_disabled();
> @@ -703,9 +704,9 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> trace_contention_begin(lock, LCB_F_MUTEX);
> }
>
> - raw_spin_lock(&lock->wait_lock);
> + raw_spin_lock_irqsave(&lock->wait_lock, flags);
> }
> - raw_spin_lock(&lock->wait_lock);
> + raw_spin_lock_irqsave(&lock->wait_lock, flags);
> acquired:
> __set_current_state(TASK_RUNNING);
>
> @@ -732,7 +733,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> if (ww_ctx)
> ww_mutex_lock_acquired(ww, ww_ctx);
>
> - raw_spin_unlock(&lock->wait_lock);
> + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
> if (ww_ctx)
> ww_ctx_wake(ww_ctx);
> preempt_enable();
> @@ -743,7 +744,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> __mutex_remove_waiter(lock, &waiter);
> err_early_kill:
> trace_contention_end(lock, ret);
> - raw_spin_unlock(&lock->wait_lock);
> + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
> debug_mutex_free_waiter(&waiter);
> mutex_release(&lock->dep_map, ip);
> if (ww_ctx)
> @@ -915,6 +916,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
> struct task_struct *next = NULL;
> DEFINE_WAKE_Q(wake_q);
> unsigned long owner;
> + unsigned long flags;
>
> mutex_release(&lock->dep_map, ip);
>
> @@ -941,7 +943,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
> }
> }
>
> - raw_spin_lock(&lock->wait_lock);
> + raw_spin_lock_irqsave(&lock->wait_lock, flags);
> debug_mutex_unlock(lock);
> if (!list_empty(&lock->wait_list)) {
> /* get the first entry from the wait-list: */
> @@ -959,7 +961,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
> __mutex_handoff(lock, next);
>
> preempt_disable();
> - raw_spin_unlock(&lock->wait_lock);
> + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
>
> wake_up_q(&wake_q);
> preempt_enable();
> diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
> index dfc174cd96c6..7edd55d10f87 100644
> --- a/kernel/locking/ww_mutex.h
> +++ b/kernel/locking/ww_mutex.h
> @@ -70,14 +70,14 @@ __ww_mutex_has_waiters(struct mutex *lock)
> return atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS;
> }
>
> -static inline void lock_wait_lock(struct mutex *lock)
> +static inline void lock_wait_lock(struct mutex *lock, unsigned long *flags)
> {
> - raw_spin_lock(&lock->wait_lock);
> + raw_spin_lock_irqsave(&lock->wait_lock, *flags);
> }
>
> -static inline void unlock_wait_lock(struct mutex *lock)
> +static inline void unlock_wait_lock(struct mutex *lock, unsigned long flags)
> {
> - raw_spin_unlock(&lock->wait_lock);
> + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
> }
>
> static inline void lockdep_assert_wait_lock_held(struct mutex *lock)
> @@ -144,14 +144,14 @@ __ww_mutex_has_waiters(struct rt_mutex *lock)
> return rt_mutex_has_waiters(&lock->rtmutex);
> }
>
> -static inline void lock_wait_lock(struct rt_mutex *lock)
> +static inline void lock_wait_lock(struct rt_mutex *lock, unsigned long *flags)
> {
> - raw_spin_lock(&lock->rtmutex.wait_lock);
> + raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags);
> }
>
> -static inline void unlock_wait_lock(struct rt_mutex *lock)
> +static inline void unlock_wait_lock(struct rt_mutex *lock, flags)
> {
> - raw_spin_unlock(&lock->rtmutex.wait_lock);
> + raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, flags);
> }
>
> static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)
> @@ -382,6 +382,8 @@ __ww_mutex_check_waiters(struct MUTEX *lock, struct ww_acquire_ctx *ww_ctx)
> static __always_inline void
> ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
> {
> + unsigned long flags;
> +
> ww_mutex_lock_acquired(lock, ctx);
>
> /*
> @@ -409,9 +411,9 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
> * Uh oh, we raced in fastpath, check if any of the waiters need to
> * die or wound us.
> */
> - lock_wait_lock(&lock->base);
> + lock_wait_lock(&lock->base, &flags);
> __ww_mutex_check_waiters(&lock->base, ctx);
> - unlock_wait_lock(&lock->base);
> + unlock_wait_lock(&lock->base, flags);
> }
>
> static __always_inline int
> --
> 2.38.0.rc1.362.ged0d419d3c-goog
>
next prev parent reply other threads:[~2022-10-13 4:30 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 21:44 [RFC PATCH 00/11] Reviving the Proxy Execution Series Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 01/11] locking/ww_mutex: Remove wakeups from under mutex::wait_lock Connor O'Brien
2022-10-04 16:01 ` Waiman Long
2022-10-12 23:54 ` Joel Fernandes
2022-10-20 18:43 ` Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 02/11] locking/mutex: Rework task_struct::blocked_on Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 03/11] kernel/locking: Add p->blocked_on wrapper Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 04/11] locking/mutex: make mutex::wait_lock irq safe Connor O'Brien
2022-10-13 4:30 ` Joel Fernandes [this message]
2022-10-03 21:44 ` [RFC PATCH 05/11] sched: Split scheduler execution context Connor O'Brien
2022-10-14 17:01 ` Joel Fernandes
2022-10-19 17:17 ` Valentin Schneider
2022-10-20 18:43 ` Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 06/11] kernel/locking: Expose mutex_owner() Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 07/11] sched: Add proxy execution Connor O'Brien
2022-10-12 1:54 ` Joel Fernandes
2022-10-12 9:46 ` Juri Lelli
2022-10-14 17:07 ` Joel Fernandes
2022-10-15 13:53 ` Peter Zijlstra
2022-10-16 20:48 ` Steven Rostedt
2022-10-17 4:03 ` Joel Fernandes
2022-10-17 7:26 ` Peter Zijlstra
2022-10-24 22:33 ` Qais Yousef
2022-10-25 11:19 ` Joel Fernandes
2022-10-25 22:10 ` Qais Yousef
2022-10-15 15:28 ` Peter Zijlstra
2022-10-15 15:08 ` Peter Zijlstra
2022-10-15 15:10 ` Peter Zijlstra
2022-10-15 15:47 ` Peter Zijlstra
2022-10-24 10:13 ` Dietmar Eggemann
2022-10-29 3:31 ` Joel Fernandes
2022-10-31 16:39 ` Dietmar Eggemann
2022-10-31 18:00 ` Joel Fernandes
2022-11-04 17:09 ` Dietmar Eggemann
2022-11-21 0:22 ` Joel Fernandes
2022-11-21 1:49 ` Joel Fernandes
2022-11-21 3:59 ` Joel Fernandes
2022-11-22 18:45 ` Joel Fernandes
2023-01-09 8:51 ` Chen Yu
2022-10-03 21:44 ` [RFC PATCH 08/11] sched: Fixup task CPUs for potential proxies Connor O'Brien
2022-10-03 21:44 ` [RFC PATCH 09/11] sched/rt: Fix proxy/current (push,pull)ability Connor O'Brien
2022-10-10 11:40 ` Valentin Schneider
2022-10-14 22:32 ` Connor O'Brien
2022-10-19 17:05 ` Valentin Schneider
2022-10-20 13:30 ` Juri Lelli
2022-10-20 16:14 ` Valentin Schneider
2022-10-21 2:22 ` Connor O'Brien
2022-10-03 21:45 ` [RFC PATCH 10/11] torture: support randomized shuffling for proxy exec testing Connor O'Brien
2022-11-12 16:54 ` Joel Fernandes
2022-11-14 20:44 ` Connor O'Brien
2022-11-15 16:02 ` Joel Fernandes
2022-10-03 21:45 ` [RFC PATCH 11/11] locktorture: support nested mutexes Connor O'Brien
2022-10-06 9:59 ` [RFC PATCH 00/11] Reviving the Proxy Execution Series Juri Lelli
2022-10-06 10:07 ` Peter Zijlstra
2022-10-06 12:14 ` Juri Lelli
2022-10-15 15:44 ` Peter Zijlstra
2022-10-17 2:23 ` Joel Fernandes
2022-10-19 11:43 ` Qais Yousef
2022-10-19 12:23 ` Joel Fernandes
2022-10-19 13:41 ` Juri Lelli
2022-10-19 13:51 ` Joel Fernandes
2022-10-19 19:30 ` Qais Yousef
2022-10-20 8:51 ` Joel Fernandes
2022-10-17 3:25 ` Chengming Zhou
2022-10-17 3:56 ` Joel Fernandes
2022-10-17 4:26 ` Chengming Zhou
2022-10-17 12:27 ` Joel Fernandes
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