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([39.120.225.141]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23499615432sm18290195ad.246.2025.05.27.13.05.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 May 2025 13:05:38 -0700 (PDT) From: Gyeyoung Baek To: Jonathan Cameron Cc: David Lechner , =?UTF-8?q?Nuno=20S=C3=A1?= , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Gyeyoung Baek Subject: [PATCH] iio: trigger: Avoid data race Date: Wed, 28 May 2025 05:05:34 +0900 Message-ID: <20250527200534.98689-1-gye976@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A data race could occur between `atomic_read()` and `atomic_set()` Use `atomic_cmpxchg_relaxed()` to group them atomically. Previously the main logic was executed when `use_count` is 0. Now it returns early when `use_count` is not 0. Signed-off-by: Gyeyoung Baek --- drivers/iio/industrialio-trigger.c | 38 +++++++++++++----------------- 1 file changed, 17 insertions(+), 21 deletions(-) diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-= trigger.c index 54416a384232..33a565037e0d 100644 --- a/drivers/iio/industrialio-trigger.c +++ b/drivers/iio/industrialio-trigger.c @@ -194,17 +194,15 @@ static void iio_trigger_notify_done_atomic(struct iio= _trigger *trig) */ void iio_trigger_poll(struct iio_trigger *trig) { - int i; - - if (!atomic_read(&trig->use_count)) { - atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER); - - for (i =3D 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) { - if (trig->subirqs[i].enabled) - generic_handle_irq(trig->subirq_base + i); - else - iio_trigger_notify_done_atomic(trig); - } + if (atomic_cmpxchg_relaxed(&trig->use_count, 0, + CONFIG_IIO_CONSUMERS_PER_TRIGGER)) + return; + + for (int i =3D 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) { + if (trig->subirqs[i].enabled) + generic_handle_irq(trig->subirq_base + i); + else + iio_trigger_notify_done_atomic(trig); } } EXPORT_SYMBOL(iio_trigger_poll); @@ -225,17 +223,15 @@ EXPORT_SYMBOL(iio_trigger_generic_data_rdy_poll); */ void iio_trigger_poll_nested(struct iio_trigger *trig) { - int i; - - if (!atomic_read(&trig->use_count)) { - atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER); + if (atomic_cmpxchg_relaxed(&trig->use_count, 0, + CONFIG_IIO_CONSUMERS_PER_TRIGGER)) + return; =20 - for (i =3D 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) { - if (trig->subirqs[i].enabled) - handle_nested_irq(trig->subirq_base + i); - else - iio_trigger_notify_done(trig); - } + for (int i =3D 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) { + if (trig->subirqs[i].enabled) + handle_nested_irq(trig->subirq_base + i); + else + iio_trigger_notify_done(trig); } } EXPORT_SYMBOL(iio_trigger_poll_nested); --=20 2.43.0