[openib-general] [PATCH -stable] IB/ucm: Fix deadlock in cleanup

[Michael S. Tsirkin]

ib_ucm_cleanup_events() holds file_mutex while calling ib_destroy_cm_id().
This can deadlock since ib_destroy_cm_id() flushes event handlers, and
ib_ucm_event_handler() needs file_mutex, too.  Therefore, drop the
file_mutex during the call to ib_destroy_cm_id().

Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd at cisco.com>
Acked-by: Sean Hefty <sean.hefty at intel.com>

---

Hello, -stable team!
This patch backports commit f469b2626f48829c06e40ac799c1edf62b12048e to 2.6.19.
Please consider it for 2.6.19.y - this fixes a deadlock reproduced here at Mellanox.

diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
index 1f4f2d2..f15220a 100644
--- a/drivers/infiniband/core/ucm.c
+++ b/drivers/infiniband/core/ucm.c
@@ -161,12 +161,14 @@ static void ib_ucm_cleanup_events(struct ib_ucm_context *ctx)
 				    struct ib_ucm_event, ctx_list);
 		list_del(&uevent->file_list);
 		list_del(&uevent->ctx_list);
+		mutex_unlock(&ctx->file->file_mutex);
 
 		/* clear incoming connections. */
 		if (ib_ucm_new_cm_id(uevent->resp.event))
 			ib_destroy_cm_id(uevent->cm_id);
 
 		kfree(uevent);
+		mutex_lock(&ctx->file->file_mutex);
 	}
 	mutex_unlock(&ctx->file->file_mutex);
 }

-- 
MST