linux-kernel - [PATCH 3.16 268/306] powerpc/eeh: Fix deadlock when PE frozen state can't be cleared

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Message-ID: <lsq.1487198500.902860744@decadent.org.uk>
Date:   Wed, 15 Feb 2017 22:41:40 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Andrew Donnellan" <andrew.donnellan@....ibm.com>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        "Pradipta Ghosh" <pradghos@...ibm.com>,
        "Russell Currey" <ruscur@...sell.cc>
Subject: [PATCH 3.16 268/306] powerpc/eeh: Fix deadlock when PE frozen
 state can't be cleared

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Donnellan <andrew.donnellan@....ibm.com>

commit 409bf7f8a02ef88db5a0f2cdcf9489914f4b8508 upstream.

In eeh_reset_device(), we take the pci_rescan_remove_lock immediately after
after we call eeh_reset_pe() to reset the PCI controller. We then call
eeh_clear_pe_frozen_state(), which can return an error. In this case, we
bail out of eeh_reset_device() without calling pci_unlock_rescan_remove().

Add a call to pci_unlock_rescan_remove() in the eeh_clear_pe_frozen_state()
error path so that we don't cause a deadlock later on.

Reported-by: Pradipta Ghosh <pradghos@...ibm.com>
Fixes: 78954700631f ("powerpc/eeh: Avoid I/O access during PE reset")
Signed-off-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
Acked-by: Russell Currey <ruscur@...sell.cc>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/kernel/eeh_driver.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -541,8 +541,10 @@ static int eeh_reset_device(struct eeh_p

 	/* Clear frozen state */
 	rc = eeh_clear_pe_frozen_state(pe);
-	if (rc)
+	if (rc) {
+		pci_unlock_rescan_remove();
 		return rc;
+	}

 	/* Give the system 5 seconds to finish running the user-space
 	 * hotplug shutdown scripts, e.g. ifdown for ethernet.  Yes,