Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269256AbUIHR3w (ORCPT ); Wed, 8 Sep 2004 13:29:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269257AbUIHR3v (ORCPT ); Wed, 8 Sep 2004 13:29:51 -0400 Received: from mail-relay-3.tiscali.it ([213.205.33.43]:23787 "EHLO mail-relay-3.tiscali.it") by vger.kernel.org with ESMTP id S269256AbUIHR3k (ORCPT ); Wed, 8 Sep 2004 13:29:40 -0400 Subject: [patch 1/1] uml:fix ubd deadlock on SMP To: akpm@osdl.org Cc: jdike@addtoit.com, linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, blaisorblade_spam@yahoo.it From: blaisorblade_spam@yahoo.it Date: Wed, 08 Sep 2004 19:25:02 +0200 Message-Id: <20040908172503.384144933@zion.localdomain> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3449 Lines: 115 Trivial: don't lock the queue spinlock when called from the request function. Since the faulty function must use spinlock in another case, double-case it. And since we will never use both functions together, let no object code be shared between them. Signed-off-by: Paolo 'Blaisorblade' Giarrusso --- uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c | 36 ++++++++++++++++----- 1 files changed, 28 insertions(+), 8 deletions(-) diff -puN arch/um/drivers/ubd_kern.c~uml-fix-ubd-deadlock arch/um/drivers/ubd_kern.c --- uml-linux-2.6.8.1/arch/um/drivers/ubd_kern.c~uml-fix-ubd-deadlock 2004-09-08 19:04:27.662926344 +0200 +++ uml-linux-2.6.8.1-paolo/arch/um/drivers/ubd_kern.c 2004-09-08 19:05:36.700431048 +0200 @@ -54,6 +54,7 @@ #include "mem.h" #include "mem_kern.h" +/*This is the queue lock. FIXME: make it per-UBD device.*/ static spinlock_t ubd_io_lock = SPIN_LOCK_UNLOCKED; static spinlock_t ubd_lock = SPIN_LOCK_UNLOCKED; @@ -396,14 +397,16 @@ int thread_fd = -1; */ int intr_count = 0; -static void ubd_finish(struct request *req, int error) +static inline void __ubd_finish(struct request *req, int error, int lock) { int nsect; if(error){ - spin_lock(&ubd_io_lock); + if (lock) + spin_lock(&ubd_io_lock); end_request(req, 0); - spin_unlock(&ubd_io_lock); + if (lock) + spin_unlock(&ubd_io_lock); return; } nsect = req->current_nr_sectors; @@ -412,11 +415,28 @@ static void ubd_finish(struct request *r req->errors = 0; req->nr_sectors -= nsect; req->current_nr_sectors = 0; - spin_lock(&ubd_io_lock); + if (lock) + spin_lock(&ubd_io_lock); end_request(req, 1); - spin_unlock(&ubd_io_lock); + if (lock) + spin_unlock(&ubd_io_lock); +} + +/* We will use only one of them, not both, i.e. ubd_finish with the io_thread + * and ubd_finish_nolock without the separate io thread, so it's better to waste + * some space to gain performance. */ + +static void ubd_finish(struct request *req, int error) +{ + __ubd_finish(req, error, 1); +} + +static void ubd_finish_nolock(struct request *req, int error) +{ + __ubd_finish(req, error, 0); } +/*Called with ubd_io_lock not held*/ static void ubd_handler(void) { struct io_thread_req req; @@ -965,6 +985,7 @@ static int prepare_mmap_request(struct u 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 +998,7 @@ static int prepare_request(struct reques 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 +1048,7 @@ static int prepare_request(struct reques 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 +1060,7 @@ static void do_ubd_request(request_queue err = prepare_request(req, &io_req); if(!err){ do_io(&io_req); - ubd_finish(req, io_req.error); + ubd_finish_nolock(req, io_req.error); } } } _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/