[stable] [11/35] aio: wake all waiters when destroying ctx

[Greg KH]

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

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

From: Roland Dreier <rol...@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 <rol...@purestorage.com>
Reviewed-by: Jeff Moyer <jmo...@redhat.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@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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