[PATCH] sound: fix hang in mpu401_uart.c

This fixes a hang in mpu401_uart.c that can occur when the mpu401 interface
is non-existent or otherwise doesn't respond to commands but we issue IO
anyway.  snd_mpu401_uart_cmd now returns an error code that is passed up
the stack so that an open() will fail immediately in such cases.

Eventually discovered after wine/cxoffice would constantly cause hard
lockups on my desktop immediately after loading (emulating Windows too
well).  Turned out that I'd recently moved my sound cards around and using
/dev/sequencer now talks to a sound card with a broken MPU.

This second version changes -EFAULT to -EIO and frees open resources on
error too.  Test booted and seems to work ok.

Signed-off-by: Jon Masters <jcm@jonmasters.org>
Cc: Jaroslav Kysela <perex@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 33 insertions, 9 deletions

diff --git a/sound/drivers/mpu401/mpu401_uart.c b/sound/drivers/mpu401/mpu401_uart.c
index 8687ae3c66b8..b49a45cbf67a 100644
--- a/sound/drivers/mpu401/mpu401_uart.c
+++ b/sound/drivers/mpu401/mpu401_uart.c
@@ -183,7 +183,8 @@ static void snd_mpu401_uart_remove_timer (struct snd_mpu401 *mpu, int input)
 
  */
 
-static void snd_mpu401_uart_cmd(struct snd_mpu401 * mpu, unsigned char cmd, int ack)
+static int snd_mpu401_uart_cmd(struct snd_mpu401 * mpu, unsigned char cmd,
+                int ack)
 {
         unsigned long flags;
         int timeout, ok;
@@ -218,9 +219,11 @@ static void snd_mpu401_uart_cmd(struct snd_mpu401 * mpu, unsigned char cmd, int
                 ok = 1;
         }
         spin_unlock_irqrestore(&mpu->input_lock, flags);
-        if (! ok)
+        if (!ok) {
                 snd_printk("cmd: 0x%x failed at 0x%lx (status = 0x%x, data = 0x%x)\n", cmd, mpu->port, mpu->read(mpu, MPU401C(mpu)), mpu->read(mpu, MPU401D(mpu)));
-        // snd_printk("cmd: 0x%x at 0x%lx (status = 0x%x, data = 0x%x)\n", cmd, mpu->port, mpu->read(mpu, MPU401C(mpu)), mpu->read(mpu, MPU401D(mpu)));
+                return 1;
+        }
+        return 0;
 }
 
 /*
@@ -235,12 +238,19 @@ static int snd_mpu401_uart_input_open(struct snd_rawmidi_substream *substream)
         if (mpu->open_input && (err = mpu->open_input(mpu)) < 0)
                 return err;
         if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode)) {
-                snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
-                snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
+                if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
+                        goto error_out;
+                if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
+                        goto error_out;
         }
         mpu->substream_input = substream;
         set_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
         return 0;
+
+error_out:
+        if (mpu->open_input && mpu->close_input)
+                mpu->close_input(mpu);
+        return -EIO;
 }
 
 static int snd_mpu401_uart_output_open(struct snd_rawmidi_substream *substream)
@@ -252,39 +262,52 @@ static int snd_mpu401_uart_output_open(struct snd_rawmidi_substream *substream)
         if (mpu->open_output && (err = mpu->open_output(mpu)) < 0)
                 return err;
         if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode)) {
-                snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
-                snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
+                if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
+                        goto error_out;
+                if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
+                        goto error_out;
         }
         mpu->substream_output = substream;
         set_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
         return 0;
+
+error_out:
+        if (mpu->open_output && mpu->close_output)
+                mpu->close_output(mpu);
+        return -EIO;
 }
 
 static int snd_mpu401_uart_input_close(struct snd_rawmidi_substream *substream)
 {
         struct snd_mpu401 *mpu;
+        int err = 0;
 
         mpu = substream->rmidi->private_data;
         clear_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
         mpu->substream_input = NULL;
         if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode))
-                snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
+                err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
         if (mpu->close_input)
                 mpu->close_input(mpu);
+        if (err)
+                return -EIO;
         return 0;
 }
 
 static int snd_mpu401_uart_output_close(struct snd_rawmidi_substream *substream)
 {
         struct snd_mpu401 *mpu;
+        int err = 0;
 
         mpu = substream->rmidi->private_data;
         clear_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
         mpu->substream_output = NULL;
         if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode))
-                snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
+                err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
         if (mpu->close_output)
                 mpu->close_output(mpu);
+        if (err)
+                return -EIO;
         return 0;
 }
 
@@ -316,6 +339,7 @@ static void snd_mpu401_uart_input_trigger(struct snd_rawmidi_substream *substrea
                         snd_mpu401_uart_remove_timer(mpu, 1);
                 clear_bit(MPU401_MODE_BIT_INPUT_TRIGGER, &mpu->mode);
         }
+
 }
 
 /*