[PATCH] drbd: fix regression 'out of mem, failed to invoke fence-peer helper'

From: Philipp Reisner
Date: Wed Jul 09 2014 - 15:19:28 EST

From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>

Since linux kernel 3.13, kthread_run() internally uses
wait_for_completion_killable(). We sometimes may use kthread_run()
while we still have a signal pending, which we used to kick our threads
out of potentially blocking network functions, causing kthread_run() to
mistake that as a new fatal signal and fail.

Fix: flush_signals() before kthread_run().

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
drivers/block/drbd/drbd_nl.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 1b35c45..3f2e167 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -544,6 +544,12 @@ void conn_try_outdate_peer_async(struct drbd_connection *connection)
struct task_struct *opa;

+ /* We may just have force_sig()'ed this thread
+ * to get it out of some blocking network function.
+ * Clear signals; otherwise kthread_run(), which internally uses
+ * wait_on_completion_killable(), will mistake our pending signal
+ * for a new fatal signal and fail. */
+ flush_signals(current);
opa = kthread_run(_try_outdate_peer_async, connection, "drbd_async_h");
if (IS_ERR(opa)) {
drbd_err(connection, "out of mem, failed to invoke fence-peer helper\n");

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