Messages in this thread Patch in this message | | | Date | Sun, 27 Aug 2006 00:59:49 +0400 | From | Oleg Nesterov <> | Subject | [PATCH RESEND] sys_ioprio_set: don't disable irqs |
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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 <oleg@tv-sign.ru>
--- 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/
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