linux-kernel - [PATCH 5.4 044/135] powerpc/eeh: Fix deadlock handling dead PHB

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Date:   Thu, 27 Feb 2020 14:36:24 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sam Bobroff <sbobroff@...ux.ibm.com>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.4 044/135] powerpc/eeh: Fix deadlock handling dead PHB

From: Sam Bobroff <sbobroff@...ux.ibm.com>

commit d4f194ed9eb9841a8f978710e4d24296f791a85b upstream.

Recovering a dead PHB can currently cause a deadlock as the PCI
rescan/remove lock is taken twice.

This is caused as part of an existing bug in
eeh_handle_special_event(). The pe is processed while traversing the
PHBs even though the pe is unrelated to the loop. This causes the pe
to be, incorrectly, processed more than once.

Untangling this section can move the pe processing out of the loop and
also outside the locked section, correcting both problems.

Fixes: 2e25505147b8 ("powerpc/eeh: Fix crash when edev->pdev changes")
Cc: stable@...r.kernel.org # 5.4+
Signed-off-by: Sam Bobroff <sbobroff@...ux.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@...ux.ibm.com>
Tested-by: Frederic Barrat <fbarrat@...ux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/0547e82dbf90ee0729a2979a8cac5c91665c621f.1581051445.git.sbobroff@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kernel/eeh_driver.c |   21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -1200,6 +1200,17 @@ void eeh_handle_special_event(void)
 			eeh_pe_state_mark(pe, EEH_PE_RECOVERING);
 			eeh_handle_normal_event(pe);
 		} else {
+			eeh_for_each_pe(pe, tmp_pe)
+				eeh_pe_for_each_dev(tmp_pe, edev, tmp_edev)
+					edev->mode &= ~EEH_DEV_NO_HANDLER;
+
+			/* Notify all devices to be down */
+			eeh_pe_state_clear(pe, EEH_PE_PRI_BUS, true);
+			eeh_set_channel_state(pe, pci_channel_io_perm_failure);
+			eeh_pe_report(
+				"error_detected(permanent failure)", pe,
+				eeh_report_failure, NULL);
+
 			pci_lock_rescan_remove();
 			list_for_each_entry(hose, &hose_list, list_node) {
 				phb_pe = eeh_phb_pe_get(hose);
@@ -1208,16 +1219,6 @@ void eeh_handle_special_event(void)
 				    (phb_pe->state & EEH_PE_RECOVERING))
 					continue;
 
-				eeh_for_each_pe(pe, tmp_pe)
-					eeh_pe_for_each_dev(tmp_pe, edev, tmp_edev)
-						edev->mode &= ~EEH_DEV_NO_HANDLER;
-
-				/* Notify all devices to be down */
-				eeh_pe_state_clear(pe, EEH_PE_PRI_BUS, true);
-				eeh_set_channel_state(pe, pci_channel_io_perm_failure);
-				eeh_pe_report(
-					"error_detected(permanent failure)", pe,
-					eeh_report_failure, NULL);
 				bus = eeh_pe_bus_get(phb_pe);
 				if (!bus) {
 					pr_err("%s: Cannot find PCI bus for "