41 lines
1.3 KiB
Diff
41 lines
1.3 KiB
Diff
From: Scott Wood <swood@redhat.com>
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Date: Fri, 4 Jan 2019 15:33:21 -0500
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Subject: [PATCH] locking/rt-mutex: Flush block plug on __down_read()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz
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__down_read() bypasses the rtmutex frontend to call
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rt_mutex_slowlock_locked() directly, and thus it needs to call
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blk_schedule_flush_flug() itself.
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Cc: stable-rt@vger.kernel.org
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Signed-off-by: Scott Wood <swood@redhat.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/locking/rwsem-rt.c | 9 +++++++++
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1 file changed, 9 insertions(+)
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--- a/kernel/locking/rwsem-rt.c
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+++ b/kernel/locking/rwsem-rt.c
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@@ -1,5 +1,6 @@
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/*
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*/
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+#include <linux/blkdev.h>
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#include <linux/rwsem.h>
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#include <linux/sched/debug.h>
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#include <linux/sched/signal.h>
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@@ -87,6 +88,14 @@ static int __sched __down_read_common(st
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if (__down_read_trylock(sem))
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return 0;
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+ /*
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+ * If rt_mutex blocks, the function sched_submit_work will not call
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+ * blk_schedule_flush_plug (because tsk_is_pi_blocked would be true).
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+ * We must call blk_schedule_flush_plug here, if we don't call it,
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+ * a deadlock in I/O may happen.
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+ */
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+ if (unlikely(blk_needs_flush_plug(current)))
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+ blk_schedule_flush_plug(current);
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might_sleep();
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raw_spin_lock_irq(&m->wait_lock);
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