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author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2009-03-26 15:24:09 +0100 |
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committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-03-26 15:24:13 +0100 |
commit | 98c1c6825247c71e3d8a9a5439ba21fce7563014 (patch) | |
tree | 6e2311aff5eefba2aaad2f09b1c11b7b2b0eceae | |
parent | e74fe0cec92439115630b51195444b89b910800a (diff) | |
download | op-kernel-dev-98c1c6825247c71e3d8a9a5439ba21fce7563014.zip op-kernel-dev-98c1c6825247c71e3d8a9a5439ba21fce7563014.tar.gz |
[S390] cio/crw: add/fix locking
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>
-rw-r--r-- | drivers/s390/cio/crw.c | 32 |
1 files changed, 23 insertions, 9 deletions
diff --git a/drivers/s390/cio/crw.c b/drivers/s390/cio/crw.c index 508f88f..d157665 100644 --- a/drivers/s390/cio/crw.c +++ b/drivers/s390/cio/crw.c @@ -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; } |