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From: Sasha Levin <Alexander.Levin@microsoft.com>
To: "stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: vkuznets <vkuznets@redhat.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 3.18 12/13] xen/manage: don't complain about an empty value in control/sysrq node
Date: Mon, 1 Oct 2018 00:41:52 +0000	[thread overview]
Message-ID: <20181001004139.147341-12-alexander.levin@microsoft.com> (raw)
In-Reply-To: <20181001004139.147341-1-alexander.levin@microsoft.com>

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit 87dffe86d406bee8782cac2db035acb9a28620a7 ]

When guest receives a sysrq request from the host it acknowledges it by
writing '\0' to control/sysrq xenstore node. This, however, make xenstore
watch fire again but xenbus_scanf() fails to parse empty value with "%c"
format string:

 sysrq: SysRq : Emergency Sync
 Emergency Sync complete
 xen:manage: Error -34 reading sysrq code in control/sysrq

Ignore -ERANGE the same way we already ignore -ENOENT, empty value in
control/sysrq is totally legal.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/xen/manage.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 77909a2c6723..101189fbf032 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -277,9 +277,11 @@ static void sysrq_handler(struct xenbus_watch *watch, const char **vec,
 		/*
 		 * The Xenstore watch fires directly after registering it and
 		 * after a suspend/resume cycle. So ENOENT is no error but
-		 * might happen in those cases.
+		 * might happen in those cases. ERANGE is observed when we get
+		 * an empty value (''), this happens when we acknowledge the
+		 * request by writing '\0' below.
 		 */
-		if (err != -ENOENT)
+		if (err != -ENOENT && err != -ERANGE)
 			pr_err("Error %d reading sysrq code in control/sysrq\n",
 			       err);
 		xenbus_transaction_end(xbt, 1);
-- 
2.17.1

  parent reply	other threads:[~2018-10-01  0:43 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-01  0:41 [PATCH AUTOSEL 3.18 01/13] usb: gadget: fotg210-udc: Fix memory leak of fotg210->ep[i] Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 02/13] pinctrl: msm: Really mask level interrupts to prevent latching Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 03/13] RDMA/ucma: check fd type in ucma_migrate_id() Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 04/13] USB: yurex: Check for truncation in yurex_read() Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 05/13] fs/cifs: suppress a string overflow warning Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 06/13] dm thin metadata: try to avoid ever aborting transactions Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 07/13] arch/hexagon: fix kernel/dma.c build warning Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 08/13] hexagon: modify ffs() and fls() to return int Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 09/13] r8169: Clear RTL_FLAG_TASK_*_PENDING when clearing RTL_FLAG_TASK_ENABLED Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 10/13] s390/qeth: don't dump past end of unknown HW header Sasha Levin
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 11/13] cifs: read overflow in is_valid_oplock_break() Sasha Levin
2018-10-01  0:41 ` Sasha Levin [this message]
2018-10-01  0:41 ` [PATCH AUTOSEL 3.18 13/13] xen: fix GCC warning and remove duplicate EVTCHN_ROW/EVTCHN_COL usage Sasha Levin

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