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[S390] cio/crw: add/fix locking

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The crw_unregister_handler uses xchg + synchronize_sched when
unregistering a crw_handler.
This doesn't protect crw_collect_info to potentially jump to NULL since
it has unlocked code like this:

if (crw_handlers[i])
        crw_handlers[i](NULL, NULL, 1);

So add a mutex which protects the crw handler array for changes.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2009-03-26 15:24:09 +01:00 committed by Martin Schwidefsky
parent e74fe0cec9
commit 98c1c68252
1 changed files with 23 additions and 9 deletions
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32
drivers/s390/cio/crw.c
View file

@ -9,11 +9,13 @@
*/
#include <linux/semaphore.h>
#include <linux/mutex.h>
#include <linux/kthread.h>
#include <linux/init.h>
#include <asm/crw.h>
static struct semaphore crw_semaphore;
static DEFINE_MUTEX(crw_handler_mutex);
static crw_handler_t crw_handlers[NR_RSCS];
/**
@ -25,11 +27,17 @@ static crw_handler_t crw_handlers[NR_RSCS];
*/
int crw_register_handler(int rsc, crw_handler_t handler)
{
int rc = 0;
if ((rsc < 0) || (rsc >= NR_RSCS))
return -EINVAL;
if (!cmpxchg(&crw_handlers[rsc], NULL, handler))
return 0;
return -EBUSY;
mutex_lock(&crw_handler_mutex);
if (crw_handlers[rsc])
rc = -EBUSY;
else
crw_handlers[rsc] = handler;
mutex_unlock(&crw_handler_mutex);
return rc;
}
/**
@ -40,8 +48,9 @@ void crw_unregister_handler(int rsc)
{
if ((rsc < 0) || (rsc >= NR_RSCS))
return;
xchg(&crw_handlers[rsc], NULL);
synchronize_sched();
mutex_lock(&crw_handler_mutex);
crw_handlers[rsc] = NULL;
mutex_unlock(&crw_handler_mutex);
}
/*
@ -58,6 +67,8 @@ repeat:
ignore = down_interruptible(&crw_semaphore);
chain = 0;
while (1) {
crw_handler_t handler;
if (unlikely(chain > 1)) {
struct crw tmp_crw;
@ -90,10 +101,12 @@ repeat:
int i;
pr_debug("%s: crw overflow detected!\n", __func__);
mutex_lock(&crw_handler_mutex);
for (i = 0; i < NR_RSCS; i++) {
if (crw_handlers[i])
crw_handlers[i](NULL, NULL, 1);
}
mutex_unlock(&crw_handler_mutex);
chain = 0;
continue;
}
@ -101,10 +114,11 @@ repeat:
chain++;
continue;
}
if (crw_handlers[crw[chain].rsc])
crw_handlers[crw[chain].rsc](&crw[0],
chain ? &crw[1] : NULL,
0);
mutex_lock(&crw_handler_mutex);
handler = crw_handlers[crw[chain].rsc];
if (handler)
handler(&crw[0], chain ? &crw[1] : NULL, 0);
mutex_unlock(&crw_handler_mutex);
/* chain is always 0 or 1 here. */
chain = crw[chain].chn ? chain + 1 : 0;
}