108 lines
3.4 KiB
Diff
108 lines
3.4 KiB
Diff
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From 7d7e185125f3936a075cec881c70a732ab232736 Mon Sep 17 00:00:00 2001
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Thu, 23 Mar 2017 15:56:14 +0100
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Subject: [PATCH 024/365] rtmutex: Fix more prio comparisons
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Upstream commit 19830e55247cddb3f46f1bf60b8e245593491bea
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There was a pure ->prio comparison left in try_to_wake_rt_mutex(),
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convert it to use rt_mutex_waiter_less(), noting that greater-or-equal
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is not-less (both in kernel priority view).
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This necessitated the introduction of cmp_task() which creates a
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pointer to an unnamed stack variable of struct rt_mutex_waiter type to
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compare against tasks.
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With this, we can now also create and employ rt_mutex_waiter_equal().
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Reviewed-and-tested-by: Juri Lelli <juri.lelli@arm.com>
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: juri.lelli@arm.com
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Cc: bigeasy@linutronix.de
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Cc: xlpang@redhat.com
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Cc: rostedt@goodmis.org
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Cc: mathieu.desnoyers@efficios.com
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Cc: jdesfossez@efficios.com
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Cc: bristot@redhat.com
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Link: http://lkml.kernel.org/r/20170323150216.455584638@infradead.org
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/locking/rtmutex.c | 32 +++++++++++++++++++++++++++++---
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1 file changed, 29 insertions(+), 3 deletions(-)
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diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
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index e275b8148db9..a8202c772907 100644
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -222,6 +222,12 @@ static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock,
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}
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#endif
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+/*
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+ * Only use with rt_mutex_waiter_{less,equal}()
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+ */
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+#define task_to_waiter(p) \
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+ &(struct rt_mutex_waiter){ .prio = (p)->prio, .deadline = (p)->dl.deadline }
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+
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static inline int
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rt_mutex_waiter_less(struct rt_mutex_waiter *left,
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struct rt_mutex_waiter *right)
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@@ -241,6 +247,25 @@ rt_mutex_waiter_less(struct rt_mutex_waiter *left,
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return 0;
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}
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+static inline int
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+rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
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+ struct rt_mutex_waiter *right)
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+{
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+ if (left->prio != right->prio)
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+ return 0;
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+
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+ /*
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+ * If both waiters have dl_prio(), we check the deadlines of the
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+ * associated tasks.
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+ * If left waiter has a dl_prio(), and we didn't return 0 above,
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+ * then right waiter has a dl_prio() too.
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+ */
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+ if (dl_prio(left->prio))
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+ return left->deadline == right->deadline;
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+
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+ return 1;
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+}
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+
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static void
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rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
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{
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@@ -551,7 +576,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
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* enabled we continue, but stop the requeueing in the chain
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* walk.
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*/
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- if (waiter->prio == task->prio && !dl_task(task)) {
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+ if (rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
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if (!detect_deadlock)
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goto out_unlock_pi;
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else
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@@ -854,7 +879,8 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
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* the top waiter priority (kernel view),
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* @task lost.
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*/
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- if (task->prio >= rt_mutex_top_waiter(lock)->prio)
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+ if (!rt_mutex_waiter_less(task_to_waiter(task),
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+ rt_mutex_top_waiter(lock)))
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return 0;
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/*
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@@ -1117,7 +1143,7 @@ void rt_mutex_adjust_pi(struct task_struct *task)
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raw_spin_lock_irqsave(&task->pi_lock, flags);
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waiter = task->pi_blocked_on;
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- if (!waiter || (waiter->prio == task->prio && !dl_prio(task->prio))) {
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+ if (!waiter || rt_mutex_waiter_equal(waiter, task_to_waiter(task))) {
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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return;
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}
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--
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2.28.0
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