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Date: Wed, 20 Sep 2023 07:36:10 -0000
From: "tip-bot2 for Sebastian Andrzej Siewior" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Crystal Wood <swood@...hat.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/rtmutex: Use rt_mutex specific scheduler helpers
The following commit has been merged into the locking/core branch of tip:
Commit-ID: d14f9e930b9073de264c106bf04968286ef9b3a4
Gitweb: https://git.kernel.org/tip/d14f9e930b9073de264c106bf04968286ef9b3a4
Author: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Fri, 08 Sep 2023 18:22:52 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 20 Sep 2023 09:31:13 +02:00
locking/rtmutex: Use rt_mutex specific scheduler helpers
Have rt_mutex use the rt_mutex specific scheduler helpers to avoid
recursion vs rtlock on the PI state.
[[ peterz: adapted to new names ]]
Reported-by: Crystal Wood <swood@...hat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20230908162254.999499-6-bigeasy@linutronix.de
---
kernel/futex/pi.c | 11 +++++++++++
kernel/locking/rtmutex.c | 14 ++++++++++++--
kernel/locking/rwbase_rt.c | 6 ++++++
kernel/locking/rwsem.c | 8 +++++++-
kernel/locking/spinlock_rt.c | 4 ++++
5 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/kernel/futex/pi.c b/kernel/futex/pi.c
index ce2889f..f8e65b2 100644
--- a/kernel/futex/pi.c
+++ b/kernel/futex/pi.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/slab.h>
+#include <linux/sched/rt.h>
#include <linux/sched/task.h>
#include "futex.h"
@@ -1002,6 +1003,12 @@ retry_private:
goto no_block;
}
+ /*
+ * Must be done before we enqueue the waiter, here is unfortunately
+ * under the hb lock, but that *should* work because it does nothing.
+ */
+ rt_mutex_pre_schedule();
+
rt_mutex_init_waiter(&rt_waiter);
/*
@@ -1052,6 +1059,10 @@ cleanup:
if (ret && !rt_mutex_cleanup_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter))
ret = 0;
+ /*
+ * Waiter is unqueued.
+ */
+ rt_mutex_post_schedule();
no_block:
/*
* Fixup the pi_state owner and possibly acquire the lock if we
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index bcec053..a3fe05d 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1632,7 +1632,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
raw_spin_unlock_irq(&lock->wait_lock);
if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner))
- schedule();
+ rt_mutex_schedule();
raw_spin_lock_irq(&lock->wait_lock);
set_current_state(state);
@@ -1661,7 +1661,7 @@ static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock,
WARN(1, "rtmutex deadlock detected\n");
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
- schedule();
+ rt_mutex_schedule();
}
}
@@ -1757,6 +1757,15 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
int ret;
/*
+ * Do all pre-schedule work here, before we queue a waiter and invoke
+ * PI -- any such work that trips on rtlock (PREEMPT_RT spinlock) would
+ * otherwise recurse back into task_blocks_on_rt_mutex() through
+ * rtlock_slowlock() and will then enqueue a second waiter for this
+ * same task and things get really confusing real fast.
+ */
+ rt_mutex_pre_schedule();
+
+ /*
* Technically we could use raw_spin_[un]lock_irq() here, but this can
* be called in early boot if the cmpxchg() fast path is disabled
* (debug, no architecture support). In this case we will acquire the
@@ -1767,6 +1776,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
raw_spin_lock_irqsave(&lock->wait_lock, flags);
ret = __rt_mutex_slowlock_locked(lock, ww_ctx, state);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
+ rt_mutex_post_schedule();
return ret;
}
diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c
index 25ec023..c7258cb 100644
--- a/kernel/locking/rwbase_rt.c
+++ b/kernel/locking/rwbase_rt.c
@@ -71,6 +71,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb,
struct rt_mutex_base *rtm = &rwb->rtmutex;
int ret;
+ rwbase_pre_schedule();
raw_spin_lock_irq(&rtm->wait_lock);
/*
@@ -125,6 +126,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb,
rwbase_rtmutex_unlock(rtm);
trace_contention_end(rwb, ret);
+ rwbase_post_schedule();
return ret;
}
@@ -237,6 +239,8 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb,
/* Force readers into slow path */
atomic_sub(READER_BIAS, &rwb->readers);
+ rwbase_pre_schedule();
+
raw_spin_lock_irqsave(&rtm->wait_lock, flags);
if (__rwbase_write_trylock(rwb))
goto out_unlock;
@@ -248,6 +252,7 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb,
if (rwbase_signal_pending_state(state, current)) {
rwbase_restore_current_state();
__rwbase_write_unlock(rwb, 0, flags);
+ rwbase_post_schedule();
trace_contention_end(rwb, -EINTR);
return -EINTR;
}
@@ -266,6 +271,7 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb,
out_unlock:
raw_spin_unlock_irqrestore(&rtm->wait_lock, flags);
+ rwbase_post_schedule();
return 0;
}
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 9eabd58..2340b6d 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1427,8 +1427,14 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
#define rwbase_signal_pending_state(state, current) \
signal_pending_state(state, current)
+#define rwbase_pre_schedule() \
+ rt_mutex_pre_schedule()
+
#define rwbase_schedule() \
- schedule()
+ rt_mutex_schedule()
+
+#define rwbase_post_schedule() \
+ rt_mutex_post_schedule()
#include "rwbase_rt.c"
diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c
index 48a19ed..842037b 100644
--- a/kernel/locking/spinlock_rt.c
+++ b/kernel/locking/spinlock_rt.c
@@ -184,9 +184,13 @@ static __always_inline int rwbase_rtmutex_trylock(struct rt_mutex_base *rtm)
#define rwbase_signal_pending_state(state, current) (0)
+#define rwbase_pre_schedule()
+
#define rwbase_schedule() \
schedule_rtlock()
+#define rwbase_post_schedule()
+
#include "rwbase_rt.c"
/*
* The common functions which get wrapped into the rwlock API.
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