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authorHefty, Sean <sean.hefty@intel.com>2012-03-02 00:01:19 +0000
committerRoland Dreier <roland@purestorage.com>2012-03-05 12:27:57 -0800
commit186834b5de69a89ba6cc846e7259451ced689b64 (patch)
tree805956214ca42d697264938080d362d1384f9dd6 /drivers/infiniband/core
parent6b21d18ed50c7d145220b0724ea7f2613abf0f95 (diff)
RDMA/ucma: Fix AB-BA deadlock
When we destroy a cm_id, we must purge associated events from the event queue. If the cm_id is for a listen request, we also purge corresponding pending connect requests. This requires destroying the cm_id's associated with the connect requests by calling rdma_destroy_id(). rdma_destroy_id() blocks until all outstanding callbacks have completed. The issue is that we hold file->mut while purging events from the event queue. We also acquire file->mut in our event handler. Calling rdma_destroy_id() while holding file->mut can lead to a deadlock, since the event handler callback cannot acquire file->mut, which prevents rdma_destroy_id() from completing. Fix this by moving events to purge from the event queue to a temporary list. We can then release file->mut and call rdma_destroy_id() outside of holding any locks. Bug report by Or Gerlitz <ogerlitz@mellanox.com>: [ INFO: possible circular locking dependency detected ] 3.3.0-rc5-00008-g79f1e43-dirty #34 Tainted: G I tgtd/9018 is trying to acquire lock: (&id_priv->handler_mutex){+.+.+.}, at: [<ffffffffa0359a41>] rdma_destroy_id+0x33/0x1f0 [rdma_cm] but task is already holding lock: (&file->mut){+.+.+.}, at: [<ffffffffa02470fe>] ucma_free_ctx+0xb6/0x196 [rdma_ucm] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&file->mut){+.+.+.}: [<ffffffff810682f3>] lock_acquire+0xf0/0x116 [<ffffffff8135f179>] mutex_lock_nested+0x64/0x2e6 [<ffffffffa0247636>] ucma_event_handler+0x148/0x1dc [rdma_ucm] [<ffffffffa035a79a>] cma_ib_handler+0x1a7/0x1f7 [rdma_cm] [<ffffffffa0333e88>] cm_process_work+0x32/0x119 [ib_cm] [<ffffffffa03362ab>] cm_work_handler+0xfb8/0xfe5 [ib_cm] [<ffffffff810423e2>] process_one_work+0x2bd/0x4a6 [<ffffffff810429e2>] worker_thread+0x1d6/0x350 [<ffffffff810462a6>] kthread+0x84/0x8c [<ffffffff81369624>] kernel_thread_helper+0x4/0x10 -> #0 (&id_priv->handler_mutex){+.+.+.}: [<ffffffff81067b86>] __lock_acquire+0x10d5/0x1752 [<ffffffff810682f3>] lock_acquire+0xf0/0x116 [<ffffffff8135f179>] mutex_lock_nested+0x64/0x2e6 [<ffffffffa0359a41>] rdma_destroy_id+0x33/0x1f0 [rdma_cm] [<ffffffffa024715f>] ucma_free_ctx+0x117/0x196 [rdma_ucm] [<ffffffffa0247255>] ucma_close+0x77/0xb4 [rdma_ucm] [<ffffffff810df6ef>] fput+0x117/0x1cf [<ffffffff810dc76e>] filp_close+0x6d/0x78 [<ffffffff8102b667>] put_files_struct+0xbd/0x17d [<ffffffff8102b76d>] exit_files+0x46/0x4e [<ffffffff8102d057>] do_exit+0x299/0x75d [<ffffffff8102d599>] do_group_exit+0x7e/0xa9 [<ffffffff8103ae4b>] get_signal_to_deliver+0x536/0x555 [<ffffffff81001717>] do_signal+0x39/0x634 [<ffffffff81001d39>] do_notify_resume+0x27/0x69 [<ffffffff81361c03>] retint_signal+0x46/0x83 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&file->mut); lock(&id_priv->handler_mutex); lock(&file->mut); lock(&id_priv->handler_mutex); *** DEADLOCK *** 1 lock held by tgtd/9018: #0: (&file->mut){+.+.+.}, at: [<ffffffffa02470fe>] ucma_free_ctx+0xb6/0x196 [rdma_ucm] stack backtrace: Pid: 9018, comm: tgtd Tainted: G I 3.3.0-rc5-00008-g79f1e43-dirty #34 Call Trace: [<ffffffff81029e9c>] ? console_unlock+0x18e/0x207 [<ffffffff81066433>] print_circular_bug+0x28e/0x29f [<ffffffff81067b86>] __lock_acquire+0x10d5/0x1752 [<ffffffff810682f3>] lock_acquire+0xf0/0x116 [<ffffffffa0359a41>] ? rdma_destroy_id+0x33/0x1f0 [rdma_cm] [<ffffffff8135f179>] mutex_lock_nested+0x64/0x2e6 [<ffffffffa0359a41>] ? rdma_destroy_id+0x33/0x1f0 [rdma_cm] [<ffffffff8106546d>] ? trace_hardirqs_on_caller+0x11e/0x155 [<ffffffff810654b1>] ? trace_hardirqs_on+0xd/0xf [<ffffffffa0359a41>] rdma_destroy_id+0x33/0x1f0 [rdma_cm] [<ffffffffa024715f>] ucma_free_ctx+0x117/0x196 [rdma_ucm] [<ffffffffa0247255>] ucma_close+0x77/0xb4 [rdma_ucm] [<ffffffff810df6ef>] fput+0x117/0x1cf [<ffffffff810dc76e>] filp_close+0x6d/0x78 [<ffffffff8102b667>] put_files_struct+0xbd/0x17d [<ffffffff8102b5cc>] ? put_files_struct+0x22/0x17d [<ffffffff8102b76d>] exit_files+0x46/0x4e [<ffffffff8102d057>] do_exit+0x299/0x75d [<ffffffff8102d599>] do_group_exit+0x7e/0xa9 [<ffffffff8103ae4b>] get_signal_to_deliver+0x536/0x555 [<ffffffff810654b1>] ? trace_hardirqs_on+0xd/0xf [<ffffffff81001717>] do_signal+0x39/0x634 [<ffffffff8135e037>] ? printk+0x3c/0x45 [<ffffffff8106546d>] ? trace_hardirqs_on_caller+0x11e/0x155 [<ffffffff810654b1>] ? trace_hardirqs_on+0xd/0xf [<ffffffff81361803>] ? _raw_spin_unlock_irq+0x2b/0x40 [<ffffffff81039011>] ? set_current_blocked+0x44/0x49 [<ffffffff81361bce>] ? retint_signal+0x11/0x83 [<ffffffff81001d39>] do_notify_resume+0x27/0x69 [<ffffffff8118a1fe>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff81361c03>] retint_signal+0x46/0x83 Signed-off-by: Sean Hefty <sean.hefty@intel.com> Signed-off-by: Roland Dreier <roland@purestorage.com>
Diffstat (limited to 'drivers/infiniband/core')
-rw-r--r--drivers/infiniband/core/ucma.c37
1 files changed, 18 insertions, 19 deletions
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 5034a87cc72..5861cdb22b7 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -449,24 +449,6 @@ static void ucma_cleanup_multicast(struct ucma_context *ctx)
mutex_unlock(&mut);
}
-static void ucma_cleanup_events(struct ucma_context *ctx)
-{
- struct ucma_event *uevent, *tmp;
-
- list_for_each_entry_safe(uevent, tmp, &ctx->file->event_list, list) {
- if (uevent->ctx != ctx)
- continue;
-
- list_del(&uevent->list);
-
- /* clear incoming connections. */
- if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST)
- rdma_destroy_id(uevent->cm_id);
-
- kfree(uevent);
- }
-}
-
static void ucma_cleanup_mc_events(struct ucma_multicast *mc)
{
struct ucma_event *uevent, *tmp;
@@ -480,9 +462,16 @@ static void ucma_cleanup_mc_events(struct ucma_multicast *mc)
}
}
+/*
+ * We cannot hold file->mut when calling rdma_destroy_id() or we can
+ * deadlock. We also acquire file->mut in ucma_event_handler(), and
+ * rdma_destroy_id() will wait until all callbacks have completed.
+ */
static int ucma_free_ctx(struct ucma_context *ctx)
{
int events_reported;
+ struct ucma_event *uevent, *tmp;
+ LIST_HEAD(list);
/* No new events will be generated after destroying the id. */
rdma_destroy_id(ctx->cm_id);
@@ -491,10 +480,20 @@ static int ucma_free_ctx(struct ucma_context *ctx)
/* Cleanup events not yet reported to the user. */
mutex_lock(&ctx->file->mut);
- ucma_cleanup_events(ctx);
+ list_for_each_entry_safe(uevent, tmp, &ctx->file->event_list, list) {
+ if (uevent->ctx == ctx)
+ list_move_tail(&uevent->list, &list);
+ }
list_del(&ctx->list);
mutex_unlock(&ctx->file->mut);
+ list_for_each_entry_safe(uevent, tmp, &list, list) {
+ list_del(&uevent->list);
+ if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST)
+ rdma_destroy_id(uevent->cm_id);
+ kfree(uevent);
+ }
+
events_reported = ctx->events_reported;
kfree(ctx);
return events_reported;