[PATCH 2/2] cpufreq/powernv: Fix unsafe notifiers

From: Oliver O'Halloran <oohall@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
	Oliver O'Halloran <oohall@gmail.com>
Subject: [PATCH 2/2] cpufreq/powernv: Fix unsafe notifiers
Date: Thu,  6 Feb 2020 17:26:22 +1100	[thread overview]
Message-ID: <20200206062622.28235-2-oohall@gmail.com> (raw)
In-Reply-To: <20200206062622.28235-1-oohall@gmail.com>

The PowerNV cpufreq driver registers two notifiers: one to catch throttle
messages from the OCC and one to bump the CPU frequency back to normal
before a reboot. Both require the cpufreq driver to be registered in order
to function since the notifier callbacks use various cpufreq_*() functions.

Right now we register both notifiers before we've initialised the driver.
This seems to work, but we should head off any protential problems by
registering the notifiers after the driver is initialised.

Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
---
 drivers/cpufreq/powernv-cpufreq.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 1806b1d..03798c4 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1114,9 +1114,6 @@ static int __init powernv_cpufreq_init(void)
 	if (rc)
 		goto out;
 
-	register_reboot_notifier(&powernv_cpufreq_reboot_nb);
-	opal_message_notifier_register(OPAL_MSG_OCC, &powernv_cpufreq_opal_nb);
-
 	if (powernv_pstate_info.wof_enabled)
 		powernv_cpufreq_driver.boost_enabled = true;
 	else
@@ -1125,15 +1122,17 @@ static int __init powernv_cpufreq_init(void)
 	rc = cpufreq_register_driver(&powernv_cpufreq_driver);
 	if (rc) {
 		pr_info("Failed to register the cpufreq driver (%d)\n", rc);
-		goto cleanup_notifiers;
+		goto cleanup;
 	}
 
 	if (powernv_pstate_info.wof_enabled)
 		cpufreq_enable_boost_support();
 
+	register_reboot_notifier(&powernv_cpufreq_reboot_nb);
+	opal_message_notifier_register(OPAL_MSG_OCC, &powernv_cpufreq_opal_nb);
+
 	return 0;
-cleanup_notifiers:
-	unregister_all_notifiers();
+cleanup:
 	clean_chip_info();
 out:
 	pr_info("Platform driver disabled. System does not support PState control\n");
-- 
2.9.5

