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Wysocki" To: Linux ACPI Cc: LKML , Linux PM , Michal Wilczynski , Zhang Rui , Srinivas Pandruvada , Daniel Lezcano Subject: [PATCH v3 5/8] ACPI: thermal: Hold thermal zone lock around trip updates Date: Tue, 25 Jul 2023 14:16:33 +0200 Message-ID: <7552439.EvYhyI6sBW@kreacher> In-Reply-To: <12254967.O9o76ZdvQC@kreacher> References: <13318886.uLZWGnKmhe@kreacher> <12254967.O9o76ZdvQC@kreacher> MIME-Version: 1.0 X-CLIENT-IP: 195.136.19.94 X-CLIENT-HOSTNAME: 195.136.19.94 X-VADE-SPAMSTATE: clean X-VADE-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedviedriedtgdehudcutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfjqffogffrnfdpggftiffpkfenuceurghilhhouhhtmecuudehtdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhephffvvefufffkjghfggfgtgesthfuredttddtjeenucfhrhhomhepfdftrghfrggvlhculfdrucghhihsohgtkhhifdcuoehrjhifsehrjhifhihsohgtkhhirdhnvghtqeenucggtffrrghtthgvrhhnpedvffeuiedtgfdvtddugeeujedtffetteegfeekffdvfedttddtuefhgeefvdejhfenucfkphepudelhedrudefiedrudelrdelgeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeduleehrddufeeirdduledrleegpdhhvghlohepkhhrvggrtghhvghrrdhlohgtrghlnhgvthdpmhgrihhlfhhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqpdhnsggprhgtphhtthhopeejpdhrtghpthhtoheplhhinhhugidqrggtphhisehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqkhgvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqphhmsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohepmhhitghhrghlrdifihhltgiihihnshhkihesihhnthgvlhdrtghomhdprhgt phhtthhopehruhhirdiihhgrnhhgsehinhhtvghlrdgtohhmpdhrtghpthhtohepshhrihhnihhvrghsrdhprghnughruhhvrggurgeslhhinhhugidrihhnthgvlhdrtghomh X-DCC--Metrics: v370.home.net.pl 1024; Body=7 Fuz1=7 Fuz2=7 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1772044269368069758 X-GMAIL-MSGID: 1772395776492306885 From: Rafael J. Wysocki There is a race condition between acpi_thermal_trips_update() and acpi_thermal_check_fn(), because the trip points may get updated while the latter is running which in theory may lead to inconsistent results. For example, if two trips are updated together, using the temperature value of one of them from before the update and the temperature value of the other one from after the update may not lead to the expected outcome. To address this, make acpi_thermal_trips_update() hold the thermal zone lock across the entire update of trip points. While at it, change the acpi_thermal_trips_update() return data type to void as that function always returns 0 anyway. Signed-off-by: Rafael J. Wysocki --- v2 -> v3: No changes. v1 -> v2: * Hold the thermal zone lock instead of thermal_check_lock around trip point updates (this also helps to protect thermal_get_trend() from using stale trip temperatures). * Add a comment documenting the purpose of the locking. * Make acpi_thermal_trips_update() void. --- drivers/acpi/thermal.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) Index: linux-pm/drivers/acpi/thermal.c =================================================================== --- linux-pm.orig/drivers/acpi/thermal.c +++ linux-pm/drivers/acpi/thermal.c @@ -190,7 +190,7 @@ static int acpi_thermal_get_polling_freq return 0; } -static int acpi_thermal_trips_update(struct acpi_thermal *tz, int flag) +static void __acpi_thermal_trips_update(struct acpi_thermal *tz, int flag) { acpi_status status; unsigned long long tmp; @@ -398,17 +398,28 @@ static int acpi_thermal_trips_update(str ACPI_THERMAL_TRIPS_EXCEPTION(flag, tz, "device"); } } +} - return 0; +static void acpi_thermal_trips_update(struct acpi_thermal *tz, int flag) +{ + /* + * The locking is needed here to protect thermal_get_trend() from using + * a stale passive trip temperature and to synchronize with the trip + * temperature updates in acpi_thermal_check_fn(). + */ + thermal_zone_device_lock(tz->thermal_zone); + + __acpi_thermal_trips_update(tz, flag); + + thermal_zone_device_unlock(tz->thermal_zone); } static int acpi_thermal_get_trip_points(struct acpi_thermal *tz) { - int i, ret = acpi_thermal_trips_update(tz, ACPI_TRIPS_INIT); bool valid; + int i; - if (ret) - return ret; + __acpi_thermal_trips_update(tz, ACPI_TRIPS_INIT); valid = tz->trips.critical.valid | tz->trips.hot.valid |