• Shailabh Nagar's avatar
    [PATCH] task delay accounting fixes · 35df17c5
    Shailabh Nagar authored
    Cleanup allocation and freeing of tsk->delays used by delay accounting.
    This solves two problems reported for delay accounting:
    1. oops in __delayacct_blkio_ticks
    Currently tsk->delays is getting freed too early in task exit which can
    cause a NULL tsk->delays to get accessed via reading of /proc/<tgid>/stats.
     The patch fixes this problem by freeing tsk->delays closer to when
    task_struct itself is freed up.  As a result, it also eliminates the use of
    tsk->delays_lock which was only being used (inadequately) to safeguard
    access to tsk->delays while a task was exiting.
    2. Possible memory leak in kernel/delayacct.c
    The patch cleans up tsk->delays allocations after a bad fork which was
    missing earlier.
    The patch has been tested to fix the problems listed above and stress
    tested with rapid calls to delay accounting's taskstats command interface
    (which is the other path that can access the same data, besides the /proc
    interface causing the oops above).
    Signed-off-by: default avatarShailabh Nagar <nagar@watson.ibm.com>
    Cc: Balbir Singh <balbir@in.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
exit.c 41.7 KB