linux-kernel - [PATCH 2/3] ipmi: Add timeout waiting for device GUID

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Message-Id: <1599495937-10654-2-git-send-email-markubo@amazon.com>
Date:   Mon,  7 Sep 2020 18:25:36 +0200
From:   Markus Boehme <markubo@...zon.com>
To:     Corey Minyard <minyard@....org>,
        openipmi-developer@...ts.sourceforge.net
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Stefan Nuernberger <snu@...zon.com>,
        SeongJae Park <sjpark@...zon.com>, Amit Shah <aams@...zon.com>,
        Markus Boehme <markubo@...zon.com>
Subject: [PATCH 2/3] ipmi: Add timeout waiting for device GUID

We have observed hosts with misbehaving BMCs that receive a Get Device
GUID command but don't respond. This leads to an indefinite wait in the
ipmi_msghandler's __get_guid function, showing up as hung task messages
for modprobe.

According to IPMI 2.0 specification chapter 20, the implementation of
the Get Device GUID command is optional. Therefore, add a timeout to
waiting for its response and treat the lack of one the same as missing a
device GUID.

Signed-off-by: Stefan Nuernberger <snu@...zon.com>
Signed-off-by: Markus Boehme <markubo@...zon.com>
---
 drivers/char/ipmi/ipmi_msghandler.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 2b213c9..2a2e8b2 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -3184,18 +3184,26 @@ static void guid_handler(struct ipmi_smi *intf, struct ipmi_recv_msg *msg)
 
 static void __get_guid(struct ipmi_smi *intf)
 {
-	int rv;
+	long rv;
 	struct bmc_device *bmc = intf->bmc;
 
 	bmc->dyn_guid_set = 2;
 	intf->null_user_handler = guid_handler;
 	rv = send_guid_cmd(intf, 0);
-	if (rv)
+	if (rv) {
 		/* Send failed, no GUID available. */
 		bmc->dyn_guid_set = 0;
-	else
-		wait_event(intf->waitq, bmc->dyn_guid_set != 2);
+		goto out;
+	}
 
+	rv = wait_event_timeout(intf->waitq, bmc->dyn_guid_set != 2, 5 * HZ);
+	if (rv == 0) {
+		dev_warn_once(intf->si_dev,
+			      "Timed out waiting for GUID. Assuming GUID is not available.\n");
+		bmc->dyn_guid_set = 0;
+	}
+
+out:
 	/* dyn_guid_set makes the guid data available. */
 	smp_rmb();
 
-- 
2.7.4