From 83c4388af1373c62cf4bb5ce2e1c2e1ad0e1af1a Mon Sep 17 00:00:00 2001 From: "Paolo \\'Blaisorblade\\' Giarrusso" Date: Wed, 13 Oct 2004 07:31:09 -0700 Subject: [PATCH] [PATCH] uml: fix ubd deadlock on SMP From: BlaisorBlade , Chris Wright Avoid deadlocking onto the request lock in the UBD driver, i.e. don't lock the queue spinlock when called from the request function. In detail: Rename ubd_finish() to __ubd_finish() and remove ubd_io_lock from it. Add wrapper, ubd_finish(), which grabs lock before calling __ubd_finish(). Update do_ubd_request to use the lock free __ubd_finish() to avoid deadlock. Also, apparently prepare_request is called with ubd_io_lock held, so remove locks there. Signed-off-by: Chris Wright Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/drivers/ubd_kern.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index fe814aa2830d3..fb6041342995b 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -396,14 +396,13 @@ int thread_fd = -1; */ int intr_count = 0; -static void ubd_finish(struct request *req, int error) +/* call ubd_finish if you need to serialize */ +static void __ubd_finish(struct request *req, int error) { int nsect; if(error){ - spin_lock(&ubd_io_lock); end_request(req, 0); - spin_unlock(&ubd_io_lock); return; } nsect = req->current_nr_sectors; @@ -412,11 +411,17 @@ static void ubd_finish(struct request *req, int error) req->errors = 0; req->nr_sectors -= nsect; req->current_nr_sectors = 0; - spin_lock(&ubd_io_lock); end_request(req, 1); +} + +static inline void ubd_finish(struct request *req, int error) +{ + spin_lock(&ubd_io_lock); + __ubd_finish(req, error); spin_unlock(&ubd_io_lock); } +/* Called without ubd_io_lock held */ static void ubd_handler(void) { struct io_thread_req req; @@ -965,6 +970,7 @@ static int prepare_mmap_request(struct ubd *dev, int fd, __u64 offset, return(0); } +/* Called with ubd_io_lock held */ static int prepare_request(struct request *req, struct io_thread_req *io_req) { struct gendisk *disk = req->rq_disk; @@ -977,9 +983,7 @@ static int prepare_request(struct request *req, struct io_thread_req *io_req) if((rq_data_dir(req) == WRITE) && !dev->openflags.w){ printk("Write attempted on readonly ubd device %s\n", disk->disk_name); - spin_lock(&ubd_io_lock); end_request(req, 0); - spin_unlock(&ubd_io_lock); return(1); } @@ -1029,6 +1033,7 @@ static int prepare_request(struct request *req, struct io_thread_req *io_req) return(0); } +/* Called with ubd_io_lock held */ static void do_ubd_request(request_queue_t *q) { struct io_thread_req io_req; @@ -1040,7 +1045,7 @@ static void do_ubd_request(request_queue_t *q) err = prepare_request(req, &io_req); if(!err){ do_io(&io_req); - ubd_finish(req, io_req.error); + __ubd_finish(req, io_req.error); } } } -- 2.53.0