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    Subject[PATCH 2/2] compat_ioctl: do not hold BKL in handlers
    We have always called ioctl conversion handlers under the big
    kernel lock, although that is generally not necessary. In particular
    it is not needed for conversion of data structures and for calling
    sys_ioctl or do_vfs_ioctl, which will get the BKL again if needed.

    Handlers doing more than those two have been moved out, so we
    can kill off the BKL from compat_sys_ioctl. This may significantly
    improve latencies with 32 bit applications, and it avoids a common
    scenario where a thread acquires the BKL twice.

    Signed-off-by: Arnd Bergmann <>
    fs/compat_ioctl.c | 2 --
    1 files changed, 0 insertions(+), 2 deletions(-)

    diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
    index 40904c6..320786e 100644
    --- a/fs/compat_ioctl.c
    +++ b/fs/compat_ioctl.c
    @@ -2663,9 +2663,7 @@ asmlinkage long compat_sys_ioctl(unsigned int fd, unsigned int cmd,

    if (t->handler) {
    - lock_kernel();
    error = t->handler(fd, cmd, arg, filp);
    - unlock_kernel();
    goto out_fput;


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      Last update: 2009-10-14 18:29    [W:0.021 / U:37.380 seconds]
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