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ALSA: mpu401: shut down timer before freeing MPU

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When an MPU401 interface has no usable IRQ, the driver polls raw-MIDI
input and output with a timer. During raw-MIDI teardown, the timer callback
can already be running when snd_mpu401_uart_remove_timer() clears the last
mode bit and calls timer_delete(). That API neither waits for a running
callback nor prevents it from rearming the timer, and free_irq() does not
synchronize timer callbacks. snd_mpu401_uart_free() can therefore release
mpu while the timer callback still uses it.

Initialize the timer once when the MPU object is created and only rearm it
while a timer mode is active. Shut it down synchronously after freeing the
IRQ so an in-flight callback completes before mpu and its resources are
released.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Link: https://patch.msgid.link/20260927093809.681726-1-runyu.xiao@seu.edu.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Runyu Xiao 2026-09-27 17:38:09 +08:00 committed by Takashi Iwai
parent 3e9c6464da
commit 9332af5220
1 changed files with 5 additions and 3 deletions
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8
sound/drivers/mpu401/mpu401_uart.c
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@ -155,20 +155,20 @@ static void snd_mpu401_uart_timer(struct timer_list *t)
scoped_guard(spinlock_irqsave, &mpu->timer_lock) {
/*mpu->mode |= MPU401_MODE_TIMER;*/
mod_timer(&mpu->timer, 1 + jiffies);
if (mpu->timer_invoked)
mod_timer(&mpu->timer, 1 + jiffies);
}
if (mpu->rmidi)
_snd_mpu401_uart_interrupt(mpu);
}
/*
* initialize the timer callback if not programmed yet
* arm the timer if it is not already active
*/
static void snd_mpu401_uart_add_timer (struct snd_mpu401 *mpu, int input)
{
guard(spinlock_irqsave)(&mpu->timer_lock);
if (mpu->timer_invoked == 0) {
timer_setup(&mpu->timer, snd_mpu401_uart_timer, 0);
mod_timer(&mpu->timer, 1 + jiffies);
}
mpu->timer_invoked |= input ? MPU401_MODE_INPUT_TIMER :
@ -474,6 +474,7 @@ static void snd_mpu401_uart_free(struct snd_rawmidi *rmidi)
struct snd_mpu401 *mpu = rmidi->private_data;
if (mpu->irq >= 0)
free_irq(mpu->irq, (void *) mpu);
timer_shutdown_sync(&mpu->timer);
release_and_free_resource(mpu->res);
kfree(mpu);
}
@ -528,6 +529,7 @@ int snd_mpu401_uart_new(struct snd_card *card, int device,
spin_lock_init(&mpu->input_lock);
spin_lock_init(&mpu->output_lock);
spin_lock_init(&mpu->timer_lock);
timer_setup(&mpu->timer, snd_mpu401_uart_timer, 0);
mpu->hardware = hardware;
mpu->irq = -1;
mpu->rmidi = rmidi;