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Tue, 03 Feb 2026 03:36:55 -0800 (PST) Received: from localhost.localdomain ([31.206.212.157]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48305161534sm51164365e9.12.2026.02.03.03.36.54 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 03 Feb 2026 03:36:55 -0800 (PST) From: Baran Arda To: gregkh@linuxfoundation.org Cc: ovidiu.panait.oss@gmail.com, gshahrouzi@gmail.com, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, baran9arda@gmail.com Subject: [PATCH] staging: axis-fifo: fix sleep while holding mutex Date: Tue, 3 Feb 2026 14:36:51 +0300 Message-Id: <20260203113651.28154-1-baran9arda@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) 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" The driver calls wait_event_interruptible_timeout() while holding a mutex. = This can lead to a deadlock or poor performance as the mutex is held while = the process is sleeping, preventing other processes from accessing the devi= ce. This patch moves the wait_event call outside of the mutex lock in both = read and write operations. --- drivers/staging/axis-fifo/axis-fifo.c | 30 +++++++++++++-------------- 1 file changed, 15 insertions(+), 15 deletions(-) diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-f= ifo/axis-fifo.c index 509d620d6ce7..a651c59a80ea 100644 --- a/drivers/staging/axis-fifo/axis-fifo.c +++ b/drivers/staging/axis-fifo/axis-fifo.c @@ -197,11 +197,10 @@ static ssize_t axis_fifo_read(struct file *f, char __= user *buf, goto end_unlock; } } else { - /* opened in blocking mode - * wait for a packet available interrupt (or timeout) - * if nothing is currently available + /* + * Opened in blocking mode. Wait for a packet available + * interrupt (or timeout) before acquiring the lock. */ - mutex_lock(&fifo->read_lock); ret =3D wait_event_interruptible_timeout(fifo->read_queue, ioread32(fifo->base_addr + XLLF_RDFO_OFFSET), read_timeout); @@ -214,8 +213,10 @@ static ssize_t axis_fifo_read(struct file *f, char __u= ser *buf, ret); } =20 - goto end_unlock; + return ret; } + + mutex_lock(&fifo->read_lock); } =20 bytes_available =3D ioread32(fifo->base_addr + XLLF_RLR_OFFSET); @@ -340,27 +341,26 @@ static ssize_t axis_fifo_write(struct file *f, const = char __user *buf, goto end_unlock; } } else { - /* opened in blocking mode */ - - /* wait for an interrupt (or timeout) if there isn't - * currently enough room in the fifo + /* + * Opened in blocking mode. Wait for enough room in the FIFO + * (or timeout) before acquiring the lock. */ - mutex_lock(&fifo->write_lock); ret =3D wait_event_interruptible_timeout(fifo->write_queue, ioread32(fifo->base_addr + XLLF_TDFV_OFFSET) - >=3D words_to_write, + >=3D words_to_write, write_timeout); =20 if (ret <=3D 0) { - if (ret =3D=3D 0) { + if (ret =3D=3D 0) ret =3D -EAGAIN; - } else if (ret !=3D -ERESTARTSYS) { + else if (ret !=3D -ERESTARTSYS) dev_err(fifo->dt_device, "wait_event_interruptible_timeout() error in = write (ret=3D%i)\n", ret); - } =20 - goto end_unlock; + return ret; } + + mutex_lock(&fifo->write_lock); } =20 txbuf =3D vmemdup_user(buf, len); --=20 2.39.5 (Apple Git-154)