Commit d4f194ed authored Feb 07, 2020 by Sam Bobroff Committed by Michael Ellerman Feb 17, 2020

powerpc/eeh: Fix deadlock handling dead PHB



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: 2e255051 ("powerpc/eeh: Fix crash when edev->pdev changes")
Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Tested-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0547e82dbf90ee0729a2979a8cac5c91665c621f.1581051445.git.sbobroff@linux.ibm.com

parent 11a48a5a

arch/powerpc/kernel/eeh_driver.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -1184,14 +1184,6 @@ void eeh_handle_special_event(void)
		eeh_pe_state_mark(pe, EEH_PE_RECOVERING);
		eeh_handle_normal_event(pe);
		} else {
		pci_lock_rescan_remove();
		list_for_each_entry(hose, &hose_list, list_node) {
		phb_pe = eeh_phb_pe_get(hose);
		if (!phb_pe \|\|
		!(phb_pe->state & EEH_PE_ISOLATED) \|\|
		(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;
		@@ -1202,6 +1194,15 @@ void eeh_handle_special_event(void)
		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);
		if (!phb_pe \|\|
		!(phb_pe->state & EEH_PE_ISOLATED) \|\|
		(phb_pe->state & EEH_PE_RECOVERING))
		continue;

		bus = eeh_pe_bus_get(phb_pe);
		if (!bus) {
		pr_err("%s: Cannot find PCI bus for "

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