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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CH3PEPF00000010.mail.protection.outlook.com (10.167.244.41) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9891.9 via Frontend Transport; Fri, 8 May 2026 05:18:24 +0000 Received: from BLRKPRNAYAK.amd.com (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Fri, 8 May 2026 00:18:20 -0500 From: K Prateek Nayak To: Mario Limonciello , Huang Rui , "Rafael J. Wysocki" , Viresh Kumar , , CC: Perry Yuan , K Prateek Nayak Subject: [PATCH 1/6] cpufreq/amd-pstate: Grab "amd_pstate_driver_lock" when toggling dynamic_epp Date: Fri, 8 May 2026 05:17:43 +0000 Message-ID: <20260508051748.10484-2-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260508051748.10484-1-kprateek.nayak@amd.com> References: <20260508051748.10484-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PEPF00000010:EE_|IA1PR12MB8079:EE_ X-MS-Office365-Filtering-Correlation-Id: f798be31-c605-4831-dac4-08deacc13a6b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|376014|36860700016|22082099003|18002099003|56012099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(376014)(36860700016)(22082099003)(18002099003)(56012099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: qZCeRQnggdLBbPYRqCP0A+g8kA2RhhFUW5bseySExsLG+QLIiFzq20aCPOL6QNJMUWi2xbxQyXGaIOXSjrxkJ9CglmV6FUE4Op3C5ATzH/htkv1PomwvQTrim4hwIrl69r/Rj39NGaqS6gSKKE6gxjeBx5Bh3p4rkPtiOYwFL24+L7b32HCWYIwbCbpmQI7p7lxieSy064DW7b8pzkB44immEerkaW1+a5CxahWs18XdYVrByGTTwlAAzBGhlLWq56RoUUnqZ846u9j6aR4GeEZ7cVBVbYOuyG2730tenfj13ikoim9+0Pm0hESPWDp6RbMjkBM/hbr3uEDkl+gqHTH0jwTtGwOSIEbDaEI21ZIEFG4/h0MizJtpFWCX7YvqeWQE2GgsQhrt8QhP9ANu6+c9aH91kVdtD4/Gq8mF36iZgAY8Zsbs6LeSxo8mHXWr X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 May 2026 05:18:24.1448 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f798be31-c605-4831-dac4-08deacc13a6b X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CH3PEPF00000010.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8079 Concurrently changing driver mode and dynamic_epp with: echo passive > /sys/devices/system/cpu/amd_pstate/status& echo disable > /sys/devices/system/cpu/amd_pstate/dynamic_epp& hits the WARN_ON_ONCE() in static_key_disable_cpuslocked() and hangs the system since both sysfs writes are trying to do amd_pstate_change_driver_mode() without any synchronization. Grab the "amd_pstate_driver_lock" mutex when modifying "dynamic_epp" to prevent the two paths from racing with each other. Add a lockdep assertion for "amd_pstate_driver_lock" in amd_pstate_change_driver_mode() to formalize the dependency. Since "cppc_mode" is stable under "amd_pstate_driver_lock", only reload the driver when in "AMD_PSTATE_ACTIVE" mode and reject all writes when in passive or guided mode, or if the driver is not loaded, since only active mode operates on EPP. Fixes: e30ca6dd5345 ("cpufreq/amd-pstate: Add dynamic energy performance preference") Reviewed-by: Mario Limonciello Signed-off-by: K Prateek Nayak --- drivers/cpufreq/amd-pstate.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 453084c67327f..5e2d28c73294d 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -1707,6 +1707,8 @@ static int amd_pstate_change_driver_mode(int mode) { int ret; + lockdep_assert_held(&amd_pstate_driver_lock); + ret = amd_pstate_unregister_driver(0); if (ret) return ret; @@ -1821,6 +1823,13 @@ static ssize_t dynamic_epp_store(struct device *a, struct device_attribute *b, if (ret) return ret; + guard(mutex)(&amd_pstate_driver_lock); + + if (cppc_state != AMD_PSTATE_ACTIVE) { + pr_debug("dynamic_epp can only be toggled in active mode\n"); + return -EINVAL; + } + if (dynamic_epp == enabled) return -EINVAL; -- 2.34.1