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87 lines
3.3 KiB
Diff
87 lines
3.3 KiB
Diff
From 30c0fabb5665235a7e6dd945be69945e9c6dc069 Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Fri, 8 Sep 2023 18:22:49 +0200
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Subject: [PATCH 002/195] locking/rtmutex: Avoid unconditional slowpath for
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DEBUG_RT_MUTEXES
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With DEBUG_RT_MUTEXES enabled the fast-path rt_mutex_cmpxchg_acquire()
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always fails and all lock operations take the slow path.
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Provide a new helper inline rt_mutex_try_acquire() which maps to
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rt_mutex_cmpxchg_acquire() in the non-debug case. For the debug case
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it invokes rt_mutex_slowtrylock() which can acquire a non-contended
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rtmutex under full debug coverage.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Link: https://lkml.kernel.org/r/20230908162254.999499-3-bigeasy@linutronix.de
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---
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kernel/locking/rtmutex.c | 21 ++++++++++++++++++++-
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kernel/locking/ww_rt_mutex.c | 2 +-
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2 files changed, 21 insertions(+), 2 deletions(-)
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diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
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index 21db0df0eb00..bcec0533a0cc 100644
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -218,6 +218,11 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock,
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return try_cmpxchg_acquire(&lock->owner, &old, new);
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}
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+static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock)
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+{
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+ return rt_mutex_cmpxchg_acquire(lock, NULL, current);
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+}
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+
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static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
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struct task_struct *old,
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struct task_struct *new)
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@@ -297,6 +302,20 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock,
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}
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+static int __sched rt_mutex_slowtrylock(struct rt_mutex_base *lock);
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+
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+static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock)
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+{
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+ /*
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+ * With debug enabled rt_mutex_cmpxchg trylock() will always fail.
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+ *
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+ * Avoid unconditionally taking the slow path by using
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+ * rt_mutex_slow_trylock() which is covered by the debug code and can
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+ * acquire a non-contended rtmutex.
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+ */
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+ return rt_mutex_slowtrylock(lock);
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+}
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+
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static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
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struct task_struct *old,
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struct task_struct *new)
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@@ -1755,7 +1774,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
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static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
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unsigned int state)
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{
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- if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
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+ if (likely(rt_mutex_try_acquire(lock)))
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return 0;
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return rt_mutex_slowlock(lock, NULL, state);
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diff --git a/kernel/locking/ww_rt_mutex.c b/kernel/locking/ww_rt_mutex.c
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index d1473c624105..c7196de838ed 100644
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--- a/kernel/locking/ww_rt_mutex.c
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+++ b/kernel/locking/ww_rt_mutex.c
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@@ -62,7 +62,7 @@ __ww_rt_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx,
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}
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mutex_acquire_nest(&rtm->dep_map, 0, 0, nest_lock, ip);
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- if (likely(rt_mutex_cmpxchg_acquire(&rtm->rtmutex, NULL, current))) {
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+ if (likely(rt_mutex_try_acquire(&rtm->rtmutex))) {
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if (ww_ctx)
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ww_mutex_set_context_fastpath(lock, ww_ctx);
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return 0;
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--
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2.43.0
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