From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752725AbaBZLGQ (ORCPT ); Wed, 26 Feb 2014 06:06:16 -0500 Received: from moutng.kundenserver.de ([212.227.126.131]:51402 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751885AbaBZLCp (ORCPT ); Wed, 26 Feb 2014 06:02:45 -0500 From: Arnd Bergmann To: linux-kernel@vger.kernel.org Cc: Arnd Bergmann , Jens Axboe , Geert Uytterhoeven , Michael Schmitz Subject: [PATCH 01/16] ataflop: fix sleep_on races Date: Wed, 26 Feb 2014 12:01:41 +0100 Message-Id: <1393412516-3762435-2-git-send-email-arnd@arndb.de> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1393412516-3762435-1-git-send-email-arnd@arndb.de> References: <1393412516-3762435-1-git-send-email-arnd@arndb.de> X-Provags-ID: V02:K0:itjoU9LYbswT8gKRTffiPmbWJs2mf/AqJbCyGYpqhBG WNH2pmKDDkZXhGq0qffVQaDZVWCDK++Sr6lXAD6ZjAXXpWRrQ4 h079D+rjx0GW+mMHYeE6YthIhgBvi+nTc3qXtNk6efZK/Ylyl4 /Ty3YjVA37f5vvfe/E0G7kQIEvXdZMYK9scEer0gJrmXlaBDR5 IOHrRQj627LeLZ4Kv2Xv/bD4vPszDaFoCqkclvPZjK5BKU8mxY joZJAUL5XqspZWYcGhNfJ+XfI6kM310zfXGAF/PLPzsfv9j1nR 6x5Ngg7GZQ7XqWzWbGfmTeA8glXHMA9RIhzSkFEhVkfGsveJcG 0TYxWdWzWdiJmBMRllFW4cVO7ZD0sYZx6Qnsr0Ked Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sleep_on() is inherently racy, and has been deprecated for a long time. This fixes two instances in the atari floppy driver: * fdc_wait/fdc_busy becomes an open-coded mutex. We cannot use the regular mutex since it gets released in interrupt context. The open-coded version using wait_event() and cmpxchg() is equivalent to the existing code but does the checks atomically, and we can now safely check the condition with irqs enabled. * format_wait becomes a completion, which is the natural structure here. The format ioctl waits for the background task to either complete or abort. This does not attempt to fix the preexisting bug of calling schedule with local interrupts disabled. Signed-off-by: Arnd Bergmann Cc: Jens Axboe Cc: Geert Uytterhoeven Cc: Michael Schmitz --- drivers/block/ataflop.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c index 0e30c6e..96b629e 100644 --- a/drivers/block/ataflop.c +++ b/drivers/block/ataflop.c @@ -68,6 +68,8 @@ #include #include #include +#include +#include #include #include @@ -301,7 +303,7 @@ module_param_array(UserSteprate, int, NULL, 0); /* Synchronization of FDC access. */ static volatile int fdc_busy = 0; static DECLARE_WAIT_QUEUE_HEAD(fdc_wait); -static DECLARE_WAIT_QUEUE_HEAD(format_wait); +static DECLARE_COMPLETION(format_wait); static unsigned long changed_floppies = 0xff, fake_change = 0; #define CHECK_CHANGE_DELAY HZ/2 @@ -608,7 +610,7 @@ static void fd_error( void ) if (IsFormatting) { IsFormatting = 0; FormatError = 1; - wake_up( &format_wait ); + complete(&format_wait); return; } @@ -650,9 +652,8 @@ static int do_format(int drive, int type, struct atari_format_descr *desc) DPRINT(("do_format( dr=%d tr=%d he=%d offs=%d )\n", drive, desc->track, desc->head, desc->sect_offset )); + wait_event(fdc_wait, cmpxchg(&fdc_busy, 0, 1) == 0); local_irq_save(flags); - while( fdc_busy ) sleep_on( &fdc_wait ); - fdc_busy = 1; stdma_lock(floppy_irq, NULL); atari_turnon_irq( IRQ_MFP_FDC ); /* should be already, just to be sure */ local_irq_restore(flags); @@ -706,7 +707,7 @@ static int do_format(int drive, int type, struct atari_format_descr *desc) ReqSide = desc->head; do_fd_action( drive ); - sleep_on( &format_wait ); + wait_for_completion(&format_wait); redo_fd_request(); return( FormatError ? -EIO : 0 ); @@ -1229,7 +1230,7 @@ static void fd_writetrack_done( int status ) goto err_end; } - wake_up( &format_wait ); + complete(&format_wait); return; err_end: @@ -1497,8 +1498,7 @@ repeat: void do_fd_request(struct request_queue * q) { DPRINT(("do_fd_request for pid %d\n",current->pid)); - while( fdc_busy ) sleep_on( &fdc_wait ); - fdc_busy = 1; + wait_event(fdc_wait, cmpxchg(&fdc_busy, 0, 1) == 0); stdma_lock(floppy_irq, NULL); atari_disable_irq( IRQ_MFP_FDC ); -- 1.8.3.2