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Date: Tue, 9 Oct 2018 11:24:28 +0200
From: Juri Lelli <juri.lelli@...hat.com>
To: peterz@...radead.org, mingo@...hat.com
Cc: rostedt@...dmis.org, tglx@...utronix.de,
linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
alessio.balsini@...il.com, bristot@...hat.com, will.deacon@....com,
andrea.parri@...rulasolutions.com, dietmar.eggemann@....com,
patrick.bellasi@....com, henrik@...tad.us,
linux-rt-users@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>
Subject: [RFD/RFC PATCH 2/8] locking/mutex: Removes wakeups from under mutex::wait_lock
From: Peter Zijlstra <peterz@...radead.org>
In preparation to nest mutex::wait_lock under rq::lock we need to remove
wakeups from under it.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
[Heavily changed after 55f036ca7e74 ("locking: WW mutex cleanup") and
08295b3b5bee ("locking: Implement an algorithm choice for Wound-Wait
mutexes")]
Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
---
kernel/locking/mutex.c | 43 +++++++++++++++++++++++++++---------------
1 file changed, 28 insertions(+), 15 deletions(-)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index df34ce70fcde..f37402cd8496 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -338,7 +338,7 @@ __ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
*/
static bool __sched
__ww_mutex_die(struct mutex *lock, struct mutex_waiter *waiter,
- struct ww_acquire_ctx *ww_ctx)
+ struct ww_acquire_ctx *ww_ctx, struct wake_q_head *wake_q)
{
if (!ww_ctx->is_wait_die)
return false;
@@ -346,7 +346,7 @@ __ww_mutex_die(struct mutex *lock, struct mutex_waiter *waiter,
if (waiter->ww_ctx->acquired > 0 &&
__ww_ctx_stamp_after(waiter->ww_ctx, ww_ctx)) {
debug_mutex_wake_waiter(lock, waiter);
- wake_up_process(waiter->task);
+ wake_q_add(wake_q, waiter->task); // XXX
}
return true;
@@ -361,7 +361,8 @@ __ww_mutex_die(struct mutex *lock, struct mutex_waiter *waiter,
*/
static bool __ww_mutex_wound(struct mutex *lock,
struct ww_acquire_ctx *ww_ctx,
- struct ww_acquire_ctx *hold_ctx)
+ struct ww_acquire_ctx *hold_ctx,
+ struct wake_q_head *wake_q)
{
struct task_struct *owner = __mutex_owner(lock);
@@ -393,7 +394,7 @@ static bool __ww_mutex_wound(struct mutex *lock,
* wakeup pending to re-read the wounded state.
*/
if (owner != current)
- wake_up_process(owner);
+ wake_q_add(wake_q, owner); // XXX
return true;
}
@@ -414,7 +415,9 @@ static bool __ww_mutex_wound(struct mutex *lock,
* The current task must not be on the wait list.
*/
static void __sched
-__ww_mutex_check_waiters(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
+__ww_mutex_check_waiters(struct mutex *lock,
+ struct ww_acquire_ctx *ww_ctx,
+ struct wake_q_head *wake_q)
{
struct mutex_waiter *cur;
@@ -424,8 +427,8 @@ __ww_mutex_check_waiters(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
if (!cur->ww_ctx)
continue;
- if (__ww_mutex_die(lock, cur, ww_ctx) ||
- __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx))
+ if (__ww_mutex_die(lock, cur, ww_ctx, wake_q) ||
+ __ww_mutex_wound(lock, cur->ww_ctx, ww_ctx, wake_q))
break;
}
}
@@ -437,6 +440,8 @@ __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)
{
+ DEFINE_WAKE_Q(wake_q);
+
ww_mutex_lock_acquired(lock, ctx);
/*
@@ -465,8 +470,10 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
* die or wound us.
*/
raw_spin_lock(&lock->base.wait_lock);
- __ww_mutex_check_waiters(&lock->base, ctx);
+ __ww_mutex_check_waiters(&lock->base, ctx, &wake_q);
raw_spin_unlock(&lock->base.wait_lock);
+
+ wake_up_q(&wake_q);
}
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
@@ -824,7 +831,8 @@ __ww_mutex_check_kill(struct mutex *lock, struct mutex_waiter *waiter,
static inline int __sched
__ww_mutex_add_waiter(struct mutex_waiter *waiter,
struct mutex *lock,
- struct ww_acquire_ctx *ww_ctx)
+ struct ww_acquire_ctx *ww_ctx,
+ struct wake_q_head *wake_q)
{
struct mutex_waiter *cur;
struct list_head *pos;
@@ -868,7 +876,7 @@ __ww_mutex_add_waiter(struct mutex_waiter *waiter,
pos = &cur->list;
/* Wait-Die: ensure younger waiters die. */
- __ww_mutex_die(lock, cur, ww_ctx);
+ __ww_mutex_die(lock, cur, ww_ctx, wake_q);
}
__mutex_add_waiter(lock, waiter, pos);
@@ -886,7 +894,7 @@ __ww_mutex_add_waiter(struct mutex_waiter *waiter,
* such that either we or the fastpath will wound @ww->ctx.
*/
smp_mb();
- __ww_mutex_wound(lock, ww_ctx, ww->ctx);
+ __ww_mutex_wound(lock, ww_ctx, ww->ctx, wake_q);
}
return 0;
@@ -900,6 +908,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
struct lockdep_map *nest_lock, unsigned long ip,
struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
+ DEFINE_WAKE_Q(wake_q);
struct mutex_waiter waiter;
bool first = false;
struct ww_mutex *ww;
@@ -940,7 +949,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
*/
if (__mutex_trylock(lock)) {
if (use_ww_ctx && ww_ctx)
- __ww_mutex_check_waiters(lock, ww_ctx);
+ __ww_mutex_check_waiters(lock, ww_ctx, &wake_q);
goto skip_wait;
}
@@ -962,7 +971,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
* Add in stamp order, waking up waiters that must kill
* themselves.
*/
- ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
+ ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx, &wake_q);
if (ret)
goto err_early_kill;
@@ -1034,7 +1043,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
*/
if (!ww_ctx->is_wait_die &&
!__mutex_waiter_is_first(lock, &waiter))
- __ww_mutex_check_waiters(lock, ww_ctx);
+ __ww_mutex_check_waiters(lock, ww_ctx, &wake_q);
}
mutex_remove_waiter(lock, &waiter, current);
@@ -1051,6 +1060,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
ww_mutex_lock_acquired(ww, ww_ctx);
raw_spin_unlock(&lock->wait_lock);
+ wake_up_q(&wake_q);
preempt_enable();
return 0;
@@ -1061,6 +1071,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
raw_spin_unlock(&lock->wait_lock);
debug_mutex_free_waiter(&waiter);
mutex_release(&lock->dep_map, 1, ip);
+ wake_up_q(&wake_q);
preempt_enable();
return ret;
}
@@ -1244,9 +1255,11 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
if (owner & MUTEX_FLAG_HANDOFF)
__mutex_handoff(lock, next);
+ preempt_disable(); // XXX unlock->wakeup inversion like
raw_spin_unlock(&lock->wait_lock);
- wake_up_q(&wake_q);
+ wake_up_q(&wake_q); // XXX must force resched on proxy
+ preempt_enable();
}
#ifndef CONFIG_DEBUG_LOCK_ALLOC
--
2.17.1
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