Messages in this thread | | | Date | Sun, 26 Oct 2003 12:03:55 +0100 | From | Manfred Spraul <> | Subject | Re: 2.6.0-test9 and sleeping function called from invalid context |
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Andrew Morton wrote:
>What protects against concurrent execution of proc_pid_lookup() and >proc_task_lookup()? I think nothing, because one is at /proc/42 and the >other is at /proc/41/42; the parent dir inodes are different. hmm. > > Ugs. /proc/1 and /proc/1/task/1 are two different dentrys. proc_task_lookup happily overwrites task->proc_dentry. Which means the task patch broke tsk->proc_dentry. I think the cure is simple: proc_task_lookup should not write proc_dentry, only proc_pid_lookup should do that. tsk->proc_dentry is only used by proc_pid_flush: If a task exits, all entries below /proc/<pid> are stale, and a shrink_dcache_parent on the /proc/<pid> dentry recovers the memory. There is a race between in proc_pid_lookup between checking that the task is still running and setting tsk->proc_dentry, but AFAICS the race is not critical: In the worst case, the stale dentries remain around. They are never returned to user space, d_revalidate prevents that.
-- Manfred
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