linux-kernel - [PATCH 5/7] ipmi: Don't call receive handler in the panic context

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Message-ID: <20150727055516.4759.56342.stgit@softrs>
Date:	Mon, 27 Jul 2015 14:55:16 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Corey Minyard <minyard@....org>
Cc:	openipmi-developer@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/7] ipmi: Don't call receive handler in the panic context

Received handlers defined as ipmi_recv_hndl member of struct
ipmi_user_hndl can take a spinlock.  This means that if the kernel
panics while holding the lock, a deadlock may happen on the lock
while flushing queued messages in the panic context.

Calling the receive handler doesn't make much meanings in the panic
context, simply skip it to avoid possible deadlocks.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
---
 drivers/char/ipmi/ipmi_msghandler.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index e7d84482..5a2d9fe 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -744,7 +744,13 @@ static void deliver_response(struct ipmi_recv_msg *msg)
 			ipmi_inc_stat(intf, unhandled_local_responses);
 		}
 		ipmi_free_recv_msg(msg);
-	} else {
+	} else if (!oops_in_progress) {
+		/*
+		 * If we are running in the panic context, calling the
+		 * receive handler doesn't much meaning and has a deadlock
+		 * risk.  At this moment, simply skip it in that case.
+		 */
+
 		ipmi_user_t user = msg->user;
 		user->handler->ipmi_recv_hndl(msg, user->handler_data);
 	}


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