linux-kernel - [PATCH] ipmi/watchdog: fix wdog hang on panic waiting for ipmi response

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Message-Id: <20170420234947.1037-1-rlippert@google.com>
Date:   Thu, 20 Apr 2017 16:49:47 -0700
From:   Robert Lippert <roblip@...il.com>
To:     Corey Minyard <minyard@....org>
Cc:     Robert Lippert <rlippert@...gle.com>,
        openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ipmi/watchdog: fix wdog hang on panic waiting for ipmi response

Commit c49c097610fe ("ipmi: Don't call receive handler in the
panic context") means that the panic_recv_free is not called during a
panic and the atomic count does not drop to 0.

Fix this by only expecting one decrement of the atomic variable
which comes from panic_smi_free.

Signed-off-by: Robert Lippert <rlippert@...gle.com>
---

 drivers/char/ipmi/ipmi_watchdog.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_watchdog.c b/drivers/char/ipmi/ipmi_watchdog.c
index 5ca24d9b101b..d165af8abe36 100644
--- a/drivers/char/ipmi/ipmi_watchdog.c
+++ b/drivers/char/ipmi/ipmi_watchdog.c
@@ -516,7 +516,7 @@ static void panic_halt_ipmi_heartbeat(void)
 	msg.cmd = IPMI_WDOG_RESET_TIMER;
 	msg.data = NULL;
 	msg.data_len = 0;
-	atomic_add(2, &panic_done_count);
+	atomic_add(1, &panic_done_count);
 	rv = ipmi_request_supply_msgs(watchdog_user,
 				      (struct ipmi_addr *) &addr,
 				      0,
@@ -526,7 +526,7 @@ static void panic_halt_ipmi_heartbeat(void)
 				      &panic_halt_heartbeat_recv_msg,
 				      1);
 	if (rv)
-		atomic_sub(2, &panic_done_count);
+		atomic_sub(1, &panic_done_count);
 }
 
 static struct ipmi_smi_msg panic_halt_smi_msg = {
@@ -550,12 +550,12 @@ static void panic_halt_ipmi_set_timeout(void)
 	/* Wait for the messages to be free. */
 	while (atomic_read(&panic_done_count) != 0)
 		ipmi_poll_interface(watchdog_user);
-	atomic_add(2, &panic_done_count);
+	atomic_add(1, &panic_done_count);
 	rv = i_ipmi_set_timeout(&panic_halt_smi_msg,
 				&panic_halt_recv_msg,
 				&send_heartbeat_now);
 	if (rv) {
-		atomic_sub(2, &panic_done_count);
+		atomic_sub(1, &panic_done_count);
 		printk(KERN_WARNING PFX
 		       "Unable to extend the watchdog timeout.");
 	} else {
-- 
2.12.2.816.g2cccc81164-goog