34 lines
1.1 KiB
Plaintext
34 lines
1.1 KiB
Plaintext
Subject: rtmutex: Handle non enqueued waiters gracefully
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Fri, 06 Nov 2015 18:51:03 +0100
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4.1-rt5.tar.xz
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Yimin debugged that in case of a PI wakeup in progress when
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rt_mutex_start_proxy_lock() calls task_blocks_on_rt_mutex() the latter
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returns -EAGAIN and in consequence the remove_waiter() call runs into
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a BUG_ON() because there is nothing to remove.
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Guard it with rt_mutex_has_waiters(). This is a quick fix which is
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easy to backport. The proper fix is to have a central check in
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remove_waiter() so we can call it unconditionally.
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Reported-and-debugged-by: Yimin Deng <yimin11.deng@gmail.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: stable-rt@vger.kernel.org
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---
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kernel/locking/rtmutex.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/kernel/locking/rtmutex.c
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+++ b/kernel/locking/rtmutex.c
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@@ -1617,7 +1617,7 @@ int rt_mutex_start_proxy_lock(struct rt_
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ret = 0;
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}
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- if (unlikely(ret))
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+ if (ret && rt_mutex_has_waiters(lock))
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remove_waiter(lock, waiter);
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raw_spin_unlock(&lock->wait_lock);
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