Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422666AbWHZQfk (ORCPT ); Sat, 26 Aug 2006 12:35:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422670AbWHZQfk (ORCPT ); Sat, 26 Aug 2006 12:35:40 -0400 Received: from taganka54-host.corbina.net ([213.234.233.54]:32917 "EHLO screens.ru") by vger.kernel.org with ESMTP id S1422666AbWHZQfk (ORCPT ); Sat, 26 Aug 2006 12:35:40 -0400 Date: Sun, 27 Aug 2006 00:59:49 +0400 From: Oleg Nesterov To: Jens Axboe Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: [PATCH RESEND] sys_ioprio_set: don't disable irqs Message-ID: <20060826205949.GA1140@oleg> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2345 Lines: 85 It is not good to disable interrupts while traversing all tasks in the system. As I see it, sys_ioprio_get() doesn't need to do it at all, sys_ioprio_set() does it for cfq_ioc_set_ioprio(), the latter can disable irqs itself. Also, add a comment to explain why do we need tasklist_lock. Signed-off-by: Oleg Nesterov --- 2.6.18-rc4/block/cfq-iosched.c~5_setpr 2006-08-27 00:37:03.000000000 +0400 +++ 2.6.18-rc4/block/cfq-iosched.c 2006-08-27 00:38:57.000000000 +0400 @@ -1421,14 +1421,14 @@ static inline void changed_ioprio(struct } /* - * callback from sys_ioprio_set, irqs are disabled + * callback from sys_ioprio_set. */ static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio) { struct cfq_io_context *cic; struct rb_node *n; - spin_lock(&cfq_exit_lock); + spin_lock_irq(&cfq_exit_lock); n = rb_first(&ioc->cic_root); while (n != NULL) { @@ -1438,7 +1438,7 @@ static int cfq_ioc_set_ioprio(struct io_ n = rb_next(n); } - spin_unlock(&cfq_exit_lock); + spin_unlock_irq(&cfq_exit_lock); return 0; } --- 2.6.18-rc4/fs/ioprio.c~5_setpr 2006-08-27 00:37:03.000000000 +0400 +++ 2.6.18-rc4/fs/ioprio.c 2006-08-27 00:54:17.000000000 +0400 @@ -81,7 +81,12 @@ asmlinkage long sys_ioprio_set(int which } ret = -ESRCH; - read_lock_irq(&tasklist_lock); + /* + * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", + * so we can't use rcu_read_lock(). See re-copy of ->ioprio + * in copy_process(). + */ + read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: if (!who) @@ -124,7 +129,7 @@ free_uid: ret = -EINVAL; } - read_unlock_irq(&tasklist_lock); + read_unlock(&tasklist_lock); return ret; } @@ -170,7 +175,7 @@ asmlinkage long sys_ioprio_get(int which int ret = -ESRCH; int tmpio; - read_lock_irq(&tasklist_lock); + read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: if (!who) @@ -221,7 +226,7 @@ asmlinkage long sys_ioprio_get(int which ret = -EINVAL; } - read_unlock_irq(&tasklist_lock); + read_unlock(&tasklist_lock); return ret; } - 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/