Adding debian version 4.19.249-2.debian/4.19.249-2debian

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 81 insertions, 0 deletions

diff --git a/debian/patches-rt/0150-locking-rt-mutex-fix-deadlock-in-device-mapper-block.patch b/debian/patches-rt/0150-locking-rt-mutex-fix-deadlock-in-device-mapper-block.patch
new file mode 100644
index 000000000..5404d73d6
--- /dev/null
+++ b/debian/patches-rt/0150-locking-rt-mutex-fix-deadlock-in-device-mapper-block.patch
@@ -0,0 +1,81 @@
+From d6b1373a76eff772848ccbfed73baf94c807e464 Mon Sep 17 00:00:00 2001
+From: Mikulas Patocka <mpatocka@redhat.com>
+Date: Mon, 13 Nov 2017 12:56:53 -0500
+Subject: [PATCH 150/347] locking/rt-mutex: fix deadlock in device mapper /
+ block-IO
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz
+
+When some block device driver creates a bio and submits it to another
+block device driver, the bio is added to current->bio_list (in order to
+avoid unbounded recursion).
+
+However, this queuing of bios can cause deadlocks, in order to avoid them,
+device mapper registers a function flush_current_bio_list. This function
+is called when device mapper driver blocks. It redirects bios queued on
+current->bio_list to helper workqueues, so that these bios can proceed
+even if the driver is blocked.
+
+The problem with CONFIG_PREEMPT_RT_FULL is that when the device mapper
+driver blocks, it won't call flush_current_bio_list (because
+tsk_is_pi_blocked returns true in sched_submit_work), so deadlocks in
+block device stack can happen.
+
+Note that we can't call blk_schedule_flush_plug if tsk_is_pi_blocked
+returns true - that would cause
+BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
+task_blocks_on_rt_mutex when flush_current_bio_list attempts to take a
+spinlock.
+
+So the proper fix is to call blk_schedule_flush_plug in rt_mutex_fastlock,
+when fast acquire failed and when the task is about to block.
+
+CC: stable-rt@vger.kernel.org
+[bigeasy: The deadlock is not device-mapper specific, it can also occur
+          in plain EXT4]
+Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/locking/rtmutex.c | 13 +++++++++++++
+ 1 file changed, 13 insertions(+)
+
+diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
+index cc47d5aa93a1..721e3a4916d9 100644
+--- a/kernel/locking/rtmutex.c
++++ b/kernel/locking/rtmutex.c
+@@ -24,6 +24,7 @@
+ #include <linux/sched/debug.h>
+ #include <linux/timer.h>
+ #include <linux/ww_mutex.h>
++#include <linux/blkdev.h>
+ 
+ #include "rtmutex_common.h"
+ 
+@@ -1919,6 +1920,15 @@ rt_mutex_fastlock(struct rt_mutex *lock, int state,
+ 	if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
+ 		return 0;
+ 
++	/*
++	 * If rt_mutex blocks, the function sched_submit_work will not call
++	 * blk_schedule_flush_plug (because tsk_is_pi_blocked would be true).
++	 * We must call blk_schedule_flush_plug here, if we don't call it,
++	 * a deadlock in I/O may happen.
++	 */
++	if (unlikely(blk_needs_flush_plug(current)))
++		blk_schedule_flush_plug(current);
++
+ 	return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK, ww_ctx);
+ }
+ 
+@@ -1936,6 +1946,9 @@ rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
+ 	    likely(rt_mutex_cmpxchg_acquire(lock, NULL, current)))
+ 		return 0;
+ 
++	if (unlikely(blk_needs_flush_plug(current)))
++		blk_schedule_flush_plug(current);
++
+ 	return slowfn(lock, state, timeout, chwalk, ww_ctx);
+ }
+ 
+-- 
+2.36.1
+