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    Subject[11/35] aio: wake all waiters when destroying ctx
    2.6.33-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Roland Dreier <roland@purestorage.com>

    commit e91f90bb0bb10be9cc8efd09a3cf4ecffcad0db1 upstream.

    The test program below will hang because io_getevents() uses
    add_wait_queue_exclusive(), which means the wake_up() in io_destroy() only
    wakes up one of the threads. Fix this by using wake_up_all() in the aio
    code paths where we want to make sure no one gets stuck.

    // t.c -- compile with gcc -lpthread -laio t.c

    #include <libaio.h>
    #include <pthread.h>
    #include <stdio.h>
    #include <unistd.h>

    static const int nthr = 2;

    void *getev(void *ctx)
    {
    struct io_event ev;
    io_getevents(ctx, 1, 1, &ev, NULL);
    printf("io_getevents returned\n");
    return NULL;
    }

    int main(int argc, char *argv[])
    {
    io_context_t ctx = 0;
    pthread_t thread[nthr];
    int i;

    io_setup(1024, &ctx);

    for (i = 0; i < nthr; ++i)
    pthread_create(&thread[i], NULL, getev, ctx);

    sleep(1);

    io_destroy(ctx);

    for (i = 0; i < nthr; ++i)
    pthread_join(thread[i], NULL);

    return 0;
    }

    Signed-off-by: Roland Dreier <roland@purestorage.com>
    Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/aio.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/fs/aio.c
    +++ b/fs/aio.c
    @@ -511,7 +511,7 @@ static inline void really_put_req(struct
    ctx->reqs_active--;

    if (unlikely(!ctx->reqs_active && ctx->dead))
    - wake_up(&ctx->wait);
    + wake_up_all(&ctx->wait);
    }

    static void aio_fput_routine(struct work_struct *data)
    @@ -1224,7 +1224,7 @@ static void io_destroy(struct kioctx *io
    * by other CPUs at this point. Right now, we rely on the
    * locking done by the above calls to ensure this consistency.
    */
    - wake_up(&ioctx->wait);
    + wake_up_all(&ioctx->wait);
    put_ioctx(ioctx); /* once for the lookup */
    }




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