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[93.198.131.143]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-434aa7e4df1sm23289425e9.39.2024.11.27.07.00.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Nov 2024 07:00:14 -0800 (PST) From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Jonathan Cameron Cc: Lars-Peter Clausen , Michael Hennerich , Nuno Sa , Dumitru Ceclan , David Lechner , linux-iio@vger.kernel.org, Andy Shevchenko , Trevor Gamblin Subject: [PATCH v4 06/10] iio: adc: ad_sigma_delta: Fix a race condition Date: Wed, 27 Nov 2024 15:59:35 +0100 Message-ID: <20241127145929.679408-18-u.kleine-koenig@baylibre.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20241127145929.679408-12-u.kleine-koenig@baylibre.com> References: <20241127145929.679408-12-u.kleine-koenig@baylibre.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5630; i=u.kleine-koenig@baylibre.com; h=from:subject; bh=/UtxUNcu7FlfgGbbbYqeI92ekworOfOuWxMulK9vmm4=; b=owEBbQGS/pANAwAKAY+A+1h9Ev5OAcsmYgBnRzPhZ1jctnT359wUzbJNDXuiikKyGWIfPGgx0 Z+4vPzq9DCJATMEAAEKAB0WIQQ/gaxpOnoeWYmt/tOPgPtYfRL+TgUCZ0cz4QAKCRCPgPtYfRL+ Tlc0CACSa3E0ocQsqmH0c2ExJYQfJWBXyAjIKxvyC3tGUO5zz0RBmJkE+tZtbQMhnfxKVnoPh// 4nMdVkUiQjyV2lEgi4fBOuWt9xS2r6j/IYj4Ay0jdzuWSSEx/oLm/64HQSOYBL16MZhmBKPOBhB VZ6gdwgJKIz+2bhAv78aiFw6zdE6Ie8FpSlESYYptEu4gNJcDSuWPyex/uH3SqPK9Khmf/ZPkjU dxHeeYickCTap4j80mQ08AF4o73PLBPjbmsE7gdhnOv0caa15drAJa7Zs2wgZ+cJyungP5Lm3+U /gVanmnqYcuYxwLZHytZtksxuvMN5tfrPuQxK5iiYD63n8j3 X-Developer-Key: i=u.kleine-koenig@baylibre.com; a=openpgp; fpr=0D2511F322BFAB1C1580266BE2DCDD9132669BD6 The ad_sigma_delta driver helper uses irq_disable_nosync(). With that one it is possible that the irq handler still runs after the irq_disable_nosync() function call returns. Also to properly synchronize irq disabling in the different threads proper locking is needed and because it's unclear if the irq handler's irq_disable_nosync() call comes first or the one in the enabler's error path, all code locations that disable the irq must check for .irq_dis first to ensure there is exactly one disable call per enable call. So add a spinlock to the struct ad_sigma_delta and use it to synchronize irq enabling and disabling. Also only act in the irq handler if the irq is still enabled. Fixes: af3008485ea0 ("iio:adc: Add common code for ADI Sigma Delta devices") Signed-off-by: Uwe Kleine-König --- drivers/iio/adc/ad_sigma_delta.c | 56 ++++++++++++++++---------- include/linux/iio/adc/ad_sigma_delta.h | 1 + 2 files changed, 36 insertions(+), 21 deletions(-) diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c index a2efd2145373..9abde276cd17 100644 --- a/drivers/iio/adc/ad_sigma_delta.c +++ b/drivers/iio/adc/ad_sigma_delta.c @@ -202,6 +202,27 @@ int ad_sd_reset(struct ad_sigma_delta *sigma_delta, } EXPORT_SYMBOL_NS_GPL(ad_sd_reset, IIO_AD_SIGMA_DELTA); +static bool ad_sd_disable_irq(struct ad_sigma_delta *sigma_delta) +{ + guard(spinlock_irqsave)(&sigma_delta->irq_lock); + + /* It's already off, return false to indicate nothing was changed */ + if (sigma_delta->irq_dis) + return false; + + sigma_delta->irq_dis = true; + disable_irq_nosync(sigma_delta->irq_line); + return true; +} + +static void ad_sd_enable_irq(struct ad_sigma_delta *sigma_delta) +{ + guard(spinlock_irqsave)(&sigma_delta->irq_lock); + + sigma_delta->irq_dis = false; + enable_irq(sigma_delta->irq_line); +} + int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta, unsigned int mode, unsigned int channel) { @@ -221,12 +242,10 @@ int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta, if (ret < 0) goto out; - sigma_delta->irq_dis = false; - enable_irq(sigma_delta->irq_line); + ad_sd_enable_irq(sigma_delta); time_left = wait_for_completion_timeout(&sigma_delta->completion, 2 * HZ); if (time_left == 0) { - sigma_delta->irq_dis = true; - disable_irq_nosync(sigma_delta->irq_line); + ad_sd_disable_irq(sigma_delta); ret = -EIO; } else { ret = 0; @@ -294,8 +313,7 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev, ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_SINGLE); - sigma_delta->irq_dis = false; - enable_irq(sigma_delta->irq_line); + ad_sd_enable_irq(sigma_delta); ret = wait_for_completion_interruptible_timeout( &sigma_delta->completion, HZ); @@ -314,10 +332,7 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev, &raw_sample); out: - if (!sigma_delta->irq_dis) { - disable_irq_nosync(sigma_delta->irq_line); - sigma_delta->irq_dis = true; - } + ad_sd_disable_irq(sigma_delta); sigma_delta->keep_cs_asserted = false; ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE); @@ -396,8 +411,7 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev) if (ret) goto err_unlock; - sigma_delta->irq_dis = false; - enable_irq(sigma_delta->irq_line); + ad_sd_enable_irq(sigma_delta); return 0; @@ -414,10 +428,7 @@ static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev) reinit_completion(&sigma_delta->completion); wait_for_completion_timeout(&sigma_delta->completion, HZ); - if (!sigma_delta->irq_dis) { - disable_irq_nosync(sigma_delta->irq_line); - sigma_delta->irq_dis = true; - } + ad_sd_disable_irq(sigma_delta); sigma_delta->keep_cs_asserted = false; ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE); @@ -516,8 +527,7 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p) irq_handled: iio_trigger_notify_done(indio_dev->trig); - sigma_delta->irq_dis = false; - enable_irq(sigma_delta->irq_line); + ad_sd_enable_irq(sigma_delta); return IRQ_HANDLED; } @@ -551,11 +561,13 @@ static irqreturn_t ad_sd_data_rdy_trig_poll(int irq, void *private) * So read the MOSI line as GPIO (if available) and only trigger the irq * if the line is active. Without such a GPIO assume this is a valid * interrupt. + * + * Also as disable_irq_nosync() is used to disable the irq, only act if + * the irq wasn't disabled before. */ - if (!sigma_delta->rdy_gpiod || gpiod_get_value(sigma_delta->rdy_gpiod)) { + if ((!sigma_delta->rdy_gpiod || gpiod_get_value(sigma_delta->rdy_gpiod)) && + ad_sd_disable_irq(sigma_delta)) { complete(&sigma_delta->completion); - disable_irq_nosync(irq); - sigma_delta->irq_dis = true; iio_trigger_poll(sigma_delta->trig); return IRQ_HANDLED; @@ -691,6 +703,8 @@ int ad_sd_init(struct ad_sigma_delta *sigma_delta, struct iio_dev *indio_dev, } } + spin_lock_init(&sigma_delta->irq_lock); + if (info->irq_line) sigma_delta->irq_line = info->irq_line; else diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h index 126b187d70e9..f86eca6126b4 100644 --- a/include/linux/iio/adc/ad_sigma_delta.h +++ b/include/linux/iio/adc/ad_sigma_delta.h @@ -86,6 +86,7 @@ struct ad_sigma_delta { /* private: */ struct completion completion; + spinlock_t irq_lock; /* protects .irq_dis and irq en/disable state */ bool irq_dis; bool bus_locked;