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From: Zqiang <qiang.zhang1211@gmail.com>
To: tiwai@suse.com
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
	Zqiang <qiang.zhang1211@gmail.com>
Subject: [PATCH] ALSA: seq: Fix RCU stall in snd_seq_write()
Date: Tue,  2 Nov 2021 11:32:22 +0800	[thread overview]
Message-ID: <20211102033222.3849-1-qiang.zhang1211@gmail.com> (raw)

If we have a lot of cell object, this cycle may take a long time, and
trigger RCU stall. insert a conditional reschedule point to fix it.

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=9f5/1/0x4000000000000000
	softirq=16474/16475 fqs=4916
	(t=10500 jiffies g=19249 q=192515)
NMI backtrace for cpu 1
......
asm_sysvec_apic_timer_interrupt
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70
spin_unlock_irqrestore
snd_seq_prioq_cell_out+0x1dc/0x360
snd_seq_check_queue+0x1a6/0x3f0
snd_seq_enqueue_event+0x1ed/0x3e0
snd_seq_client_enqueue_event.constprop.0+0x19a/0x3c0
snd_seq_write+0x2db/0x510
vfs_write+0x1c4/0x900
ksys_write+0x171/0x1d0
do_syscall_64+0x35/0xb0

Reported-by: syzbot+bb950e68b400ab4f65f8@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
---
 sound/core/seq/seq_queue.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/core/seq/seq_queue.c b/sound/core/seq/seq_queue.c
index d6c02dea976c..f5b1e4562a64 100644
--- a/sound/core/seq/seq_queue.c
+++ b/sound/core/seq/seq_queue.c
@@ -263,6 +263,7 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop)
 		if (!cell)
 			break;
 		snd_seq_dispatch_event(cell, atomic, hop);
+		cond_resched();
 	}
 
 	/* Process time queue... */
@@ -272,6 +273,7 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop)
 		if (!cell)
 			break;
 		snd_seq_dispatch_event(cell, atomic, hop);
+		cond_resched();
 	}
 
 	/* free lock */
-- 
2.17.1


WARNING: multiple messages have this Message-ID (diff)
From: Zqiang <qiang.zhang1211@gmail.com>
To: tiwai@suse.com
Cc: alsa-devel@alsa-project.org, Zqiang <qiang.zhang1211@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] ALSA: seq: Fix RCU stall in snd_seq_write()
Date: Tue,  2 Nov 2021 11:32:22 +0800	[thread overview]
Message-ID: <20211102033222.3849-1-qiang.zhang1211@gmail.com> (raw)

If we have a lot of cell object, this cycle may take a long time, and
trigger RCU stall. insert a conditional reschedule point to fix it.

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=9f5/1/0x4000000000000000
	softirq=16474/16475 fqs=4916
	(t=10500 jiffies g=19249 q=192515)
NMI backtrace for cpu 1
......
asm_sysvec_apic_timer_interrupt
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70
spin_unlock_irqrestore
snd_seq_prioq_cell_out+0x1dc/0x360
snd_seq_check_queue+0x1a6/0x3f0
snd_seq_enqueue_event+0x1ed/0x3e0
snd_seq_client_enqueue_event.constprop.0+0x19a/0x3c0
snd_seq_write+0x2db/0x510
vfs_write+0x1c4/0x900
ksys_write+0x171/0x1d0
do_syscall_64+0x35/0xb0

Reported-by: syzbot+bb950e68b400ab4f65f8@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
---
 sound/core/seq/seq_queue.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/core/seq/seq_queue.c b/sound/core/seq/seq_queue.c
index d6c02dea976c..f5b1e4562a64 100644
--- a/sound/core/seq/seq_queue.c
+++ b/sound/core/seq/seq_queue.c
@@ -263,6 +263,7 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop)
 		if (!cell)
 			break;
 		snd_seq_dispatch_event(cell, atomic, hop);
+		cond_resched();
 	}
 
 	/* Process time queue... */
@@ -272,6 +273,7 @@ void snd_seq_check_queue(struct snd_seq_queue *q, int atomic, int hop)
 		if (!cell)
 			break;
 		snd_seq_dispatch_event(cell, atomic, hop);
+		cond_resched();
 	}
 
 	/* free lock */
-- 
2.17.1


             reply	other threads:[~2021-11-02  3:32 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-02  3:32 Zqiang [this message]
2021-11-02  3:32 ` [PATCH] ALSA: seq: Fix RCU stall in snd_seq_write() Zqiang
2021-11-02  8:33 ` Takashi Iwai
2021-11-02  8:33   ` Takashi Iwai
2021-11-02  9:41   ` Zqiang
2021-11-02  9:41     ` Zqiang
2021-11-02 10:31     ` Takashi Iwai
2021-11-02 10:31       ` Takashi Iwai
2021-11-02 11:20       ` Zqiang
2021-11-02 11:20         ` Zqiang
2021-11-02 12:27         ` Takashi Iwai
2021-11-02 12:27           ` Takashi Iwai
2021-11-03  5:41           ` Zqiang
2021-11-03  5:41             ` Zqiang

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