From patchwork Thu Jun 13 15:24:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= X-Patchwork-Id: 804017 Received: from todd.t-8ch.de (todd.t-8ch.de [159.69.126.157]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DEC0353E31; Thu, 13 Jun 2024 15:24:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=159.69.126.157 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718292299; cv=none; b=pqblUv7/HGE+djPfyM0du1b7yGi3Ldy3qZAdU2nHt7rmN3p8HjjH3YV7it7wuSOl/owB9gwYVfX0tnyPFBjgpQpVpyfN1afKKp1Nx3NjYR2DB/pcXo0To+oM4EOND/Af/7EQQrM3R2YOx2YBYCBGujIRtS3Xl8Mwvchz34mqDDs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718292299; c=relaxed/simple; bh=lkr1QctdrwBqiaLGk73+KO5d+sPtA7Bi31a8uXsZvLM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=cVOIyj5ueQLQfyeDh+TfFp9KdSZsstSJkAyFjb4fkJKLd91pAyTZWC3pj23K3NcudiSKYGz2Ggl8T5Zb2BueQrDzUu2yJfjxk46p3IUTBZusSdaF38uDwGfSDT9hAYJWUjerzYGq95Y1Fp6JX5Uj+g40rv59SUfW05qhnECUvFw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=weissschuh.net; spf=pass smtp.mailfrom=weissschuh.net; dkim=pass (1024-bit key) header.d=weissschuh.net header.i=@weissschuh.net header.b=Cnu34rAF; arc=none smtp.client-ip=159.69.126.157 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=weissschuh.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=weissschuh.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=weissschuh.net header.i=@weissschuh.net header.b="Cnu34rAF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=weissschuh.net; s=mail; t=1718292294; bh=lkr1QctdrwBqiaLGk73+KO5d+sPtA7Bi31a8uXsZvLM=; h=From:Date:Subject:To:Cc:From; b=Cnu34rAFfuzqEBAV0IjuFq/EN2ECf8/ZV5aHa4+ePvlZH+OKMghnKuChzzvAa2KHX UsiYq7xIgploRqfmtwYS4diz0VVXq/605mXxHCKZBH7hhOROomK14crNZzvbebMRt+ x7PIp4bW9gApLYTQBdejF38nyGOlAxxgmT7UTq4w= From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= Date: Thu, 13 Jun 2024 17:24:51 +0200 Subject: [PATCH v2] leds: triggers: flush pending brightness before activating trigger Precedence: bulk X-Mailing-List: linux-leds@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240613-led-trigger-flush-v2-1-f4f970799d77@weissschuh.net> X-B4-Tracking: v=1; b=H4sIAEIPa2YC/32NQQqDMBBFryKz7pSYiGBXvUdxUeMkGRAtmagtk rs39QBdvgf//QOEIpPArTog0sbCy1xAXyqw4Tl7Qh4Lg1a6Ua0yONGIKbL3FNFNqwQ0AzmjDA2 d0lB2r0iO32fz0RcOLGmJn/Niq3/2X22rsUbbqca2pN1gmvtOLCI2rOE6U4I+5/wFfRGb/rcAA AA= To: Pavel Machek , Lee Jones , Jacek Anaszewski Cc: linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, Dustin Howett , stable@vger.kernel.org, =?utf-8?q?Thoma?= =?utf-8?q?s_Wei=C3=9Fschuh?= X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1718292294; l=2694; i=linux@weissschuh.net; s=20221212; h=from:subject:message-id; bh=lkr1QctdrwBqiaLGk73+KO5d+sPtA7Bi31a8uXsZvLM=; b=BeT9bQPIN0S2PP6EGAIJapWFwWehZhBUWYDfHdhDO6u9Gytb+cpAPkWQ7AsdxmI/Gl+AsLJhQ zpM2cThQSCvDSNPdcKU0lKtFti+HZHNHX69XZIXFqyy+9t6B5UZE8pP X-Developer-Key: i=linux@weissschuh.net; a=ed25519; pk=KcycQgFPX2wGR5azS7RhpBqedglOZVgRPfdFSPB1LNw= The race fixed in timer_trig_activate() between a blocking set_brightness() call and trigger->activate() can affect any trigger. So move the call to flush_work() into led_trigger_set() where it can avoid the race for all triggers. Fixes: 0db37915d912 ("leds: avoid races with workqueue") Fixes: 8c0f693c6eff ("leds: avoid flush_work in atomic context") Cc: stable@vger.kernel.org Tested-by: Dustin L. Howett Signed-off-by: Thomas Weißschuh --- Changes in v2: - Cc stable - Add Dustin's Tested-by - Rebase against led/for-leds-next - Always execute flush_work(), similar to synchronize_rcu() - Link to v1: https://lore.kernel.org/r/20240603-led-trigger-flush-v1-1-c904c6e2fb34@weissschuh.net --- Commit 7abae7a11fc9 ("leds: trigger: Call synchronize_rcu() before calling trig->activate()") alone also solves the issue that the LED stays completely off after enabling the trigger. But there is a recognizable timeframe where it is disabled in between. Also from a correctness perspective, this seems like a coincidence and the call to flush_work() is the correct fix for that race. --- drivers/leds/led-triggers.c | 6 ++++++ drivers/leds/trigger/ledtrig-timer.c | 5 ----- 2 files changed, 6 insertions(+), 5 deletions(-) --- base-commit: 005408af25d5550e1bd22a18bf371651969c17ee change-id: 20240603-led-trigger-flush-3bef303eb902 Best regards, diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c index 59deadb86335..78eb20093b2c 100644 --- a/drivers/leds/led-triggers.c +++ b/drivers/leds/led-triggers.c @@ -201,6 +201,12 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig) */ synchronize_rcu(); + /* + * If "set brightness to 0" is pending in workqueue, + * we don't want that to be reordered after ->activate() + */ + flush_work(&led_cdev->set_brightness_work); + ret = 0; if (trig->activate) ret = trig->activate(led_cdev); diff --git a/drivers/leds/trigger/ledtrig-timer.c b/drivers/leds/trigger/ledtrig-timer.c index b4688d1d9d2b..1d213c999d40 100644 --- a/drivers/leds/trigger/ledtrig-timer.c +++ b/drivers/leds/trigger/ledtrig-timer.c @@ -110,11 +110,6 @@ static int timer_trig_activate(struct led_classdev *led_cdev) led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER; } - /* - * If "set brightness to 0" is pending in workqueue, we don't - * want that to be reordered after blink_set() - */ - flush_work(&led_cdev->set_brightness_work); led_blink_set(led_cdev, &led_cdev->blink_delay_on, &led_cdev->blink_delay_off);