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Date: Tue, 4 Jun 2024 14:33:38 +0100
From: Qais Yousef <qyousef@...alina.io>
To: John Stultz <jstultz@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Juri Lelli <juri.lelli@...hat.com>,
Joel Fernandes <joelaf@...gle.com>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Valentin Schneider <vschneid@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>,
Zimuzo Ezeozue <zezeozue@...gle.com>,
Youssef Esmat <youssefesmat@...gle.com>,
Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>,
"Paul E. McKenney" <paulmck@...nel.org>,
Metin Kaya <Metin.Kaya@....com>,
Xuewen Yan <xuewen.yan94@...il.com>,
K Prateek Nayak <kprateek.nayak@....com>,
Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
Connor O'Brien <connoro@...gle.com>
Subject: Re: [PATCH v10 2/7] locking/mutex: Make mutex::wait_lock irq safe
On 05/06/24 21:54, John Stultz wrote:
> From: Juri Lelli <juri.lelli@...hat.com>
>
> mutex::wait_lock might be nested under rq->lock.
>
> Make it irq safe then.
>
> Cc: Joel Fernandes <joelaf@...gle.com>
> Cc: Qais Yousef <qyousef@...alina.io>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
> Cc: Youssef Esmat <youssefesmat@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Cc: Metin Kaya <Metin.Kaya@....com>
> Cc: Xuewen Yan <xuewen.yan94@...il.com>
> Cc: K Prateek Nayak <kprateek.nayak@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: kernel-team@...roid.com
> Tested-by: K Prateek Nayak <kprateek.nayak@....com>
> Tested-by: Metin Kaya <metin.kaya@....com>
> Reviewed-by: Metin Kaya <metin.kaya@....com>
> Reviewed-by: Valentin Schneider <vschneid@...hat.com>
> Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> [rebase & fix {un,}lock_wait_lock helpers in ww_mutex.h]
> Signed-off-by: Connor O'Brien <connoro@...gle.com>
> Signed-off-by: John Stultz <jstultz@...gle.com>
> ---
> v3:
> * Re-added this patch after it was dropped in v2 which
> caused lockdep warnings to trip.
> v7:
> * Fix function definition for PREEMPT_RT case, as pointed out
> by Metin Kaya.
> * Fix incorrect flags handling in PREEMPT_RT case as found by
> Metin Kaya
> ---
> kernel/locking/mutex.c | 18 ++++++++++--------
> kernel/locking/ww_mutex.h | 22 +++++++++++-----------
> 2 files changed, 21 insertions(+), 19 deletions(-)
Are locking folks okay with patches 1 and 2? Is there any concern/side effect
not to pick them up? It'd be nice if they can get merged and soaked in
linux-next. Reducing the amount of patches to help this series make progress
would be appreciated - if there are no major concerns of course. Some feedback
would be very helpful either way.
Thanks!
--
Qais Yousef
>
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 4269da1f3ef5..6d843a0978a5 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -578,6 +578,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
> DEFINE_WAKE_Q(wake_q);
> struct mutex_waiter waiter;
> struct ww_mutex *ww;
> + unsigned long flags;
> int ret;
>
> if (!use_ww_ctx)
> @@ -620,7 +621,7 @@ __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.
> */
> @@ -681,7 +682,7 @@ __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);
> /* Make sure we do wakeups before calling schedule */
> if (!wake_q_empty(&wake_q)) {
> wake_up_q(&wake_q);
> @@ -707,9 +708,9 @@ __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);
>
> @@ -735,7 +736,7 @@ __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);
> wake_up_q(&wake_q);
> preempt_enable();
> return 0;
> @@ -745,7 +746,7 @@ __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);
> wake_up_q(&wake_q);
> @@ -916,6 +917,7 @@ 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);
>
> @@ -942,7 +944,7 @@ 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: */
> @@ -960,7 +962,7 @@ 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 7189c6631d90..9facc0ddfdd3 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, unsigned long *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)
> @@ -380,6 +380,7 @@ static __always_inline void
> ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
> {
> DEFINE_WAKE_Q(wake_q);
> + unsigned long flags;
>
> ww_mutex_lock_acquired(lock, ctx);
>
> @@ -408,10 +409,9 @@ 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, &wake_q);
> - unlock_wait_lock(&lock->base);
> -
> + unlock_wait_lock(&lock->base, &flags);
> wake_up_q(&wake_q);
> }
>
> --
> 2.45.0.rc1.225.g2a3ae87e7f-goog
>
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