diff options
| author | Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> | 2006-10-30 22:07:08 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-10-31 08:06:59 -0800 |
| commit | 33f775eea185e8df7701c4afc2c8fcee85c83282 (patch) | |
| tree | 5cbba5e09cba9ab84ddba06cf23e1950ffbec222 /arch/um/drivers | |
| parent | d7fb2c3865ca0f95d92e2864c3dc9220789d83f5 (diff) | |
[PATCH] uml ubd driver: ubd_io_lock usage fixup
Add some comments about requirements for ubd_io_lock and expand its use.
When an irq signals that the "controller" (i.e. another thread on the host,
which does the actual requests and is the only one blocked on I/O on the host)
has done some work, we call again the request function ourselves
(do_ubd_request).
We now do that with ubd_io_lock held - that's useful to protect against
concurrent calls to elv_next_request and so on.
XXX: Maybe we shouldn't call at all the request function. Input needed on
this. Are we supposed to plug and unplug the queue? That code "indirectly"
does that by setting a flag, called do_ubd, which makes the request function
return (it's a residual of 2.4 block layer interface).
Meanwhile, however, merge this patch, which improves things.
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/um/drivers')
| -rw-r--r-- | arch/um/drivers/ubd_kern.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index a3061ae39b3..6cd8988e8fd 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -106,6 +106,8 @@ static inline void ubd_set_bit(__u64 bit, unsigned char *data) #define DRIVER_NAME "uml-blkdev" +/* Can be taken in interrupt context, and is passed to the block layer to lock + * the request queue. Kernel side code knows that. */ static DEFINE_SPINLOCK(ubd_io_lock); static DEFINE_MUTEX(ubd_lock); @@ -497,6 +499,8 @@ static void __ubd_finish(struct request *req, int error) end_request(req, 1); } +/* Callable only from interrupt context - otherwise you need to do + * spin_lock_irq()/spin_lock_irqsave() */ static inline void ubd_finish(struct request *req, int error) { spin_lock(&ubd_io_lock); @@ -504,7 +508,7 @@ static inline void ubd_finish(struct request *req, int error) spin_unlock(&ubd_io_lock); } -/* Called without ubd_io_lock held */ +/* Called without ubd_io_lock held, and only in interrupt context. */ static void ubd_handler(void) { struct io_thread_req req; @@ -525,7 +529,9 @@ static void ubd_handler(void) ubd_finish(rq, req.error); reactivate_fd(thread_fd, UBD_IRQ); + spin_lock(&ubd_io_lock); do_ubd_request(ubd_queue); + spin_unlock(&ubd_io_lock); } static irqreturn_t ubd_intr(int irq, void *dev) |