Messages in this thread Patch in this message | | | Date | Sun, 20 Aug 2006 20:08:52 +0400 | From | Oleg Nesterov <> | Subject | [PATCH] fix? current_io_context() vs set_task_ioprio() race |
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I know nothing about io scheduler, but I suspect set_task_ioprio() is not safe.
current_io_context() initializes "struct io_context", then sets ->io_context. set_task_ioprio() running on another cpu may see the changes out of order, so ->set_ioprio(ioc) may use io_context which was not initialized properly.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- 2.6.18-rc4/block/ll_rw_blk.c~3_race 2006-07-16 01:53:08.000000000 +0400 +++ 2.6.18-rc4/block/ll_rw_blk.c 2006-08-20 19:30:10.000000000 +0400 @@ -3628,6 +3628,8 @@ struct io_context *current_io_context(gf ret->nr_batch_requests = 0; /* because this is 0 */ ret->aic = NULL; ret->cic_root.rb_node = NULL; + /* make sure set_task_ioprio() sees the settings above */ + smp_wmb(); tsk->io_context = ret; } --- 2.6.18-rc4/fs/ioprio.c~3_race 2006-08-20 19:09:08.000000000 +0400 +++ 2.6.18-rc4/fs/ioprio.c 2006-08-20 19:57:14.000000000 +0400 @@ -44,6 +44,9 @@ static int set_task_ioprio(struct task_s task->ioprio = ioprio; ioc = task->io_context; + /* see wmb() in current_io_context() */ + smp_read_barrier_depends(); + if (ioc && ioc->set_ioprio) ioc->set_ioprio(ioc, ioprio); - 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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