From 5451dab9b7f5469b1499d09e15493ca54ec0d7da Mon Sep 17 00:00:00 2001 From: Valentin Vidic Date: Thu, 19 Apr 2018 12:25:30 +0200 Subject: [PATCH] staging: pi433: cleanup tx_fifo locking pi433_write requires locking due to multiple writers. After acquiring the lock check if enough free space is available in the kfifo to write the whole message. This check should prevent partial writes to tx_fifo so kfifo_reset is not needed anymore. pi433_tx_thread is the only reader so it does not require locking after kfifo_reset is removed. Signed-off-by: Valentin Vidic Reviewed-by: Marcus Wolf Signed-off-by: Greg Kroah-Hartman --- drivers/staging/pi433/pi433_if.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/staging/pi433/pi433_if.c b/drivers/staging/pi433/pi433_if.c index d1e0ddbc79ce..2a05eff88469 100644 --- a/drivers/staging/pi433/pi433_if.c +++ b/drivers/staging/pi433/pi433_if.c @@ -87,7 +87,7 @@ struct pi433_device { /* tx related values */ STRUCT_KFIFO_REC_1(MSG_FIFO_SIZE) tx_fifo; - struct mutex tx_fifo_lock; // TODO: check, whether necessary or obsolete + struct mutex tx_fifo_lock; /* serialize userspace writers */ struct task_struct *tx_task_struct; wait_queue_head_t tx_wait_queue; u8 free_in_fifo; @@ -589,19 +589,15 @@ pi433_tx_thread(void *data) * - size of message * - message */ - mutex_lock(&device->tx_fifo_lock); - retval = kfifo_out(&device->tx_fifo, &tx_cfg, sizeof(tx_cfg)); if (retval != sizeof(tx_cfg)) { dev_dbg(device->dev, "reading tx_cfg from fifo failed: got %d byte(s), expected %d", retval, (unsigned int)sizeof(tx_cfg)); - mutex_unlock(&device->tx_fifo_lock); continue; } retval = kfifo_out(&device->tx_fifo, &size, sizeof(size_t)); if (retval != sizeof(size_t)) { dev_dbg(device->dev, "reading msg size from fifo failed: got %d, expected %d", retval, (unsigned int)sizeof(size_t)); - mutex_unlock(&device->tx_fifo_lock); continue; } @@ -634,7 +630,6 @@ pi433_tx_thread(void *data) sizeof(device->buffer) - position); dev_dbg(device->dev, "read %d message byte(s) from fifo queue.", retval); - mutex_unlock(&device->tx_fifo_lock); /* if rx is active, we need to interrupt the waiting for * incoming telegrams, to be able to send something. @@ -818,7 +813,7 @@ pi433_write(struct file *filp, const char __user *buf, struct pi433_instance *instance; struct pi433_device *device; int retval; - unsigned int copied; + unsigned int required, available, copied; instance = filp->private_data; device = instance->device; @@ -833,6 +828,16 @@ pi433_write(struct file *filp, const char __user *buf, * - message */ mutex_lock(&device->tx_fifo_lock); + + required = sizeof(instance->tx_cfg) + sizeof(size_t) + count; + available = kfifo_avail(&device->tx_fifo); + if (required > available) { + dev_dbg(device->dev, "write to fifo failed: %d bytes required but %d available", + required, available); + mutex_unlock(&device->tx_fifo_lock); + return -EAGAIN; + } + retval = kfifo_in(&device->tx_fifo, &instance->tx_cfg, sizeof(instance->tx_cfg)); if (retval != sizeof(instance->tx_cfg)) @@ -855,8 +860,8 @@ pi433_write(struct file *filp, const char __user *buf, return copied; abort: - dev_dbg(device->dev, "write to fifo failed: 0x%x", retval); - kfifo_reset(&device->tx_fifo); // TODO: maybe find a solution, not to discard already stored, valid entries + dev_warn(device->dev, + "write to fifo failed, non recoverable: 0x%x", retval); mutex_unlock(&device->tx_fifo_lock); return -EAGAIN; } -- 2.11.0