linux-kernel - [PATCH 2/3] OSS trident: fix locking around write_voice

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Message-Id: <1179083728411-git-send-email-muli@il.ibm.com>
Date:	Sun, 13 May 2007 22:15:27 +0300
From:	muli@...ibm.com
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Muli Ben-Yehuda <muli@...ibm.com>,
	tammy000@...il.com, bunk@...sta.de
Subject: [PATCH 2/3] OSS trident: fix locking around write_voice_regs

From: Muli Ben-Yehuda <muli@...ibm.com>

trident_write_voice_regs() was getting called with the card spinlock
held in only some cases. Fix it.

Explanation: we allocate a new virtual channel in open, and then we
frob some hardware registers (in write_voice_regs) for that
channel. But the hardware registers are shared with other channels,
which may be trying to frob the some registers (albeit for another
channel) via ioctl(SNDCTL_DSP_SPEED).

Fixed bugzilla.kernel.org bug #8172 (http://bugme.osdl.org/show_bug.cgi?id=8172)

Signed-off-by: Muli Ben-Yehuda <muli@...ibm.com>
Cc: tammy000@...il.com
Cc: bunk@...sta.de
---
 sound/oss/trident.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/sound/oss/trident.c b/sound/oss/trident.c
index 3e408f4..2e3e78e 100644
--- a/sound/oss/trident.c
+++ b/sound/oss/trident.c
@@ -2702,6 +2702,7 @@ trident_open(struct inode *inode, struct
 	struct trident_card *card = devs;
 	struct trident_state *state = NULL;
 	struct dmabuf *dmabuf = NULL;
+	unsigned long flags;
 
 	/* Added by Matt Wu 01-05-2001 */
 	/* TODO: there's some redundacy here wrt the check below */
@@ -2779,7 +2780,9 @@ trident_open(struct inode *inode, struct
 			/* set default channel attribute to normal playback */
 			dmabuf->channel->attribute = CHANNEL_PB;
 		}
+		spin_lock_irqsave(&card->lock, flags);
 		trident_set_dac_rate(state, 8000);
+		spin_unlock_irqrestore(&card->lock, flags);
 	}
 
 	if (file->f_mode & FMODE_READ) {
@@ -2797,7 +2800,9 @@ trident_open(struct inode *inode, struct
 			dmabuf->channel->attribute = (CHANNEL_REC | PCM_LR |
 						      MONO_MIX);
 		}
+		spin_lock_irqsave(&card->lock, flags);
 		trident_set_adc_rate(state, 8000);
+		spin_unlock_irqrestore(&card->lock, flags);
 
 		/* Added by Matt Wu 01-05-2001 */
 		if (card->pci_id == PCI_DEVICE_ID_ALI_5451)
-- 
1.4.4

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