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[S390] dasd: fix race in dasd timer handling

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In dasd_device_set_timer and dasd_block_set_timer we interpret the
return value of mod_timer in a wrong way. If the timer expires in
the small window between our check of timer_pending and the call to
mod_timer, then the timer will be set, mod_timer returns zero and
we will call add_timer for a timer that is already pending.
As del_timer and mod_timer do all the necessary checking themselves,
we can simplify our code and remove the race a the same time.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Stefan Weinhuber 2009-02-11 10:37:31 +01:00 committed by Martin Schwidefsky
parent ca0b4b7d2c
commit 48cae885d5
1 changed files with 16 additions and 30 deletions
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46
drivers/s390/block/dasd.c
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@ -57,6 +57,8 @@ static void dasd_device_tasklet(struct dasd_device *);
static void dasd_block_tasklet(struct dasd_block *);
static void do_kick_device(struct work_struct *);
static void dasd_return_cqr_cb(struct dasd_ccw_req *, void *);
static void dasd_device_timeout(unsigned long);
static void dasd_block_timeout(unsigned long);
/*
* SECTION: Operations on the device structure.
@ -99,6 +101,8 @@ struct dasd_device *dasd_alloc_device(void)
(unsigned long) device);
INIT_LIST_HEAD(&device->ccw_queue);
init_timer(&device->timer);
device->timer.function = dasd_device_timeout;
device->timer.data = (unsigned long) device;
INIT_WORK(&device->kick_work, do_kick_device);
device->state = DASD_STATE_NEW;
device->target = DASD_STATE_NEW;
@ -138,6 +142,8 @@ struct dasd_block *dasd_alloc_block(void)
INIT_LIST_HEAD(&block->ccw_queue);
spin_lock_init(&block->queue_lock);
init_timer(&block->timer);
block->timer.function = dasd_block_timeout;
block->timer.data = (unsigned long) block;
return block;
}
@ -915,19 +921,10 @@ static void dasd_device_timeout(unsigned long ptr)
*/
void dasd_device_set_timer(struct dasd_device *device, int expires)
{
if (expires == 0) {
if (timer_pending(&device->timer))
del_timer(&device->timer);
return;
}
if (timer_pending(&device->timer)) {
if (mod_timer(&device->timer, jiffies + expires))
return;
}
device->timer.function = dasd_device_timeout;
device->timer.data = (unsigned long) device;
device->timer.expires = jiffies + expires;
add_timer(&device->timer);
if (expires == 0)
del_timer(&device->timer);
else
mod_timer(&device->timer, jiffies + expires);
}
/*
@ -935,8 +932,7 @@ void dasd_device_set_timer(struct dasd_device *device, int expires)
*/
void dasd_device_clear_timer(struct dasd_device *device)
{
if (timer_pending(&device->timer))
del_timer(&device->timer);
del_timer(&device->timer);
}
static void dasd_handle_killed_request(struct ccw_device *cdev,
@ -1586,19 +1582,10 @@ static void dasd_block_timeout(unsigned long ptr)
*/
void dasd_block_set_timer(struct dasd_block *block, int expires)
{
if (expires == 0) {
if (timer_pending(&block->timer))
del_timer(&block->timer);
return;
}
if (timer_pending(&block->timer)) {
if (mod_timer(&block->timer, jiffies + expires))
return;
}
block->timer.function = dasd_block_timeout;
block->timer.data = (unsigned long) block;
block->timer.expires = jiffies + expires;
add_timer(&block->timer);
if (expires == 0)
del_timer(&block->timer);
else
mod_timer(&block->timer, jiffies + expires);
}
/*
@ -1606,8 +1593,7 @@ void dasd_block_set_timer(struct dasd_block *block, int expires)
*/
void dasd_block_clear_timer(struct dasd_block *block)
{
if (timer_pending(&block->timer))
del_timer(&block->timer);
del_timer(&block->timer);
}
/*