[PATCH] Fix sleep-while-holding-lock bug in es1968

[Arjan van de Ven]

snd_es1968_ac97_read() calls snd_es1968_ac97_wait() first outside a locked area,
and later, while holding a lock.
snd_es1968_ac97_wait() has a polling loop with a cond_resched() inside it.. which
sleeps, so the second call is invalid.

This patch adds a version of the wait function that just pure polls. While this
is not very elegant in principle, it's very likely the easiest thing to do here,
we already checked if the chip was ready (while yielding) just before, so it is
very unlikely to take a long time here.

Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
---
 sound/pci/es1968.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/sound/pci/es1968.c b/sound/pci/es1968.c
index 25ccfce..71d459d 100644
--- a/sound/pci/es1968.c
+++ b/sound/pci/es1968.c
@@ -617,6 +617,18 @@ static int snd_es1968_ac97_wait(struct es1968 *chip)
 	return 1; /* timeout */
 }
 
+static int snd_es1968_ac97_wait_poll(struct es1968 *chip)
+{
+	int timeout = 100000;
+
+	while (timeout-- > 0) {
+		if (!(inb(chip->io_port + ESM_AC97_INDEX) & 1))
+			return 0;
+	}
+	snd_printd("es1968: ac97 timeout\n");
+	return 1; /* timeout */
+}
+
 static void snd_es1968_ac97_write(struct snd_ac97 *ac97, unsigned short reg, unsigned short val)
 {
 	struct es1968 *chip = ac97->private_data;
@@ -645,7 +657,7 @@ static unsigned short snd_es1968_ac97_read(struct snd_ac97 *ac97, unsigned short
 	outb(reg | 0x80, chip->io_port + ESM_AC97_INDEX);
 	/*msleep(1);*/
 
-	if (! snd_es1968_ac97_wait(chip)) {
+	if (! snd_es1968_ac97_wait_poll(chip)) {
 		data = inw(chip->io_port + ESM_AC97_DATA);
 		/*msleep(1);*/
 	}
-- 
1.5.4.4


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