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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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