linux-kernel - [PATCH] sys_ioprio_set: don't disable irqs

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Message-ID: <20060820204345.GA5750@oleg>
Date:	Mon, 21 Aug 2006 00:43:45 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Jens Axboe <axboe@...e.de>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] sys_ioprio_set: don't disable irqs

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 cli() at all,
sys_ioprio_set() does it for cfq_ioc_set_ioprio() which can do it itself.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 2.6.18-rc4/block/cfq-iosched.c~5_setpr	2006-08-09 22:00:44.000000000 +0400
+++ 2.6.18-rc4/block/cfq-iosched.c	2006-08-20 21:23:25.000000000 +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	2006-08-20 20:16:39.000000000 +0400
+++ 2.6.18-rc4/fs/ioprio.c	2006-08-20 21:21:26.000000000 +0400
@@ -81,7 +81,7 @@ asmlinkage long sys_ioprio_set(int which
 	}
 
 	ret = -ESRCH;
-	read_lock_irq(&tasklist_lock);
+	read_lock(&tasklist_lock);
 	switch (which) {
 		case IOPRIO_WHO_PROCESS:
 			if (!who)
@@ -124,7 +124,7 @@ free_uid:
 			ret = -EINVAL;
 	}
 
-	read_unlock_irq(&tasklist_lock);
+	read_unlock(&tasklist_lock);
 	return ret;
 }
 
@@ -170,7 +170,7 @@ 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 +221,7 @@ asmlinkage long sys_ioprio_get(int which
 			ret = -EINVAL;
 	}
 
-	read_unlock_irq(&tasklist_lock);
+	read_unlock(&tasklist_lock);
 	return ret;
 }
 

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