From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965021AbWA1QCA (ORCPT ); Sat, 28 Jan 2006 11:02:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965018AbWA1QCA (ORCPT ); Sat, 28 Jan 2006 11:02:00 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:30686 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S965022AbWA1QCA (ORCPT ); Sat, 28 Jan 2006 11:02:00 -0500 Date: Sat, 28 Jan 2006 17:02:40 +0100 From: Ingo Molnar To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Arjan van de Ven Subject: Re: [patch] warn on release_region() from irq context Message-ID: <20060128160240.GA21053@elte.hu> References: <20060128144357.GA6881@elte.hu> <20060128150006.GA10660@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060128150006.GA10660@elte.hu> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > the rationale for this patch is that the lock validator (which now > tracks rwlock dependencies too, see output below) noticed that > floppy.c does a release_region() from softirq context -> ouch. I'm > working on the floppy.c fix for that. ugh. floppy.c is a mess. I did the patch below - but that's not enough, it does stupid things like request_region() and release_region() from the timer irq - so floppy.c file needs a serious redesign to fix these deadlocks :-( Ingo floppy.c does alot of irq-unsafe work within floppy_release_irq_and_dma(): free_irq(), release_region() ... so when executing in irq context, push the whole function into keventd. Signed-off-by: Ingo Molnar ---- drivers/block/floppy.c | 27 +++++++++++++++++++++++++-- 1 files changed, 25 insertions(+), 2 deletions(-) Index: linux/drivers/block/floppy.c =================================================================== --- linux.orig/drivers/block/floppy.c +++ linux/drivers/block/floppy.c @@ -561,6 +561,21 @@ static int floppy_grab_irq_and_dma(void) static void floppy_release_irq_and_dma(void); /* + * Interrupt, DMA and region freeing must not be done from IRQ + * context - e.g. irq-unregistration means /proc VFS work, region + * release takes an irq-unsafe lock, etc. So we push this work + * into keventd: + */ +static void fd_release_fn(void *data) +{ + mutex_lock(&open_lock); + floppy_release_irq_and_dma(); + mutex_unlock(&open_lock); +} + +static DECLARE_WORK(floppy_release_irq_and_dma_work, fd_release_fn, NULL); + +/* * The "reset" variable should be tested whenever an interrupt is scheduled, * after the commands have been sent. This is to ensure that the driver doesn't * get wedged when the interrupt doesn't come because of a failed command. @@ -824,7 +839,7 @@ static int set_dor(int fdc, char mask, c if (newdor & FLOPPY_MOTOR_MASK) floppy_grab_irq_and_dma(); if (olddor & FLOPPY_MOTOR_MASK) - floppy_release_irq_and_dma(); + schedule_work(&floppy_release_irq_and_dma_work); return olddor; } @@ -905,6 +920,8 @@ static int _lock_fdc(int drive, int inte set_current_state(TASK_RUNNING); remove_wait_queue(&fdc_wait, &wait); + + flush_scheduled_work(); } command_status = FD_COMMAND_NONE; @@ -938,7 +955,7 @@ static inline void unlock_fdc(void) if (elv_next_request(floppy_queue)) do_fd_request(floppy_queue); spin_unlock_irqrestore(&floppy_lock, flags); - floppy_release_irq_and_dma(); + schedule_work(&floppy_release_irq_and_dma_work); wake_up(&fdc_wait); } @@ -4628,6 +4645,12 @@ void cleanup_module(void) del_timer_sync(&fd_timer); blk_cleanup_queue(floppy_queue); + /* + * Wait for any asynchronous floppy_release_irq_and_dma() + * calls to finish first: + */ + flush_scheduled_work(); + if (usage_count) floppy_release_irq_and_dma();