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kernel/pipe: code flow cleanup

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Simplify the logic, avoid repeated conditionals, avoid superfluous
scheduler calls, make the code more efficient and easier to read.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This commit is contained in:
Nicolas Pitre 2025-01-10 17:45:44 -05:00 committed by Benjamin Cabé
parent 19a376aa88
commit 46617644e7
1 changed files with 56 additions and 82 deletions
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138
kernel/pipe.c
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@ -34,8 +34,8 @@ static inline bool pipe_empty(struct k_pipe *pipe)
return ring_buf_is_empty(&pipe->buf);
}
static inline int wait_for(_wait_q_t *waitq, struct k_pipe *pipe, k_spinlock_key_t *key,
k_timepoint_t time_limit)
static int wait_for(_wait_q_t *waitq, struct k_pipe *pipe, k_spinlock_key_t *key,
k_timepoint_t time_limit)
{
k_timeout_t timeout = sys_timepoint_timeout(time_limit);
@ -48,9 +48,7 @@ static inline int wait_for(_wait_q_t *waitq, struct k_pipe *pipe, k_spinlock_key
z_pend_curr(&pipe->lock, *key, waitq, timeout);
*key = k_spin_lock(&pipe->lock);
pipe->waiting--;
if (unlikely(pipe_closed(pipe))) {
return -EPIPE;
} else if (unlikely(pipe_resetting(pipe))) {
if (unlikely(pipe_resetting(pipe))) {
if (pipe->waiting == 0) {
pipe->flags &= ~PIPE_FLAG_RESET;
}
@ -95,58 +93,47 @@ int z_impl_k_pipe_write(struct k_pipe *pipe, const uint8_t *data, size_t len, k_
{
int rc;
size_t written = 0;
k_spinlock_key_t key;
k_timepoint_t end = sys_timepoint_calc(timeout);
k_spinlock_key_t key = k_spin_lock(&pipe->lock);
SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_pipe, write, pipe, data, len, timeout);
while (written < len) {
key = k_spin_lock(&pipe->lock);
if (unlikely(pipe_resetting(pipe))) {
rc = -ECANCELED;
goto exit;
}
for (;;) {
if (unlikely(pipe_closed(pipe))) {
k_spin_unlock(&pipe->lock, key);
rc = -EPIPE;
goto exit;
} else if (unlikely(pipe_resetting(pipe))) {
k_spin_unlock(&pipe->lock, key);
rc = -ECANCELED;
goto exit;
} else if (pipe_full(pipe)) {
rc = wait_for(&pipe->space, pipe, &key, end);
if (rc == -EAGAIN) {
/* the timeout expired */
k_spin_unlock(&pipe->lock, key);
rc = written ? written : -EAGAIN;
goto exit;
} else if (unlikely(rc != 0)) {
/* The pipe was closed or reseted while waiting for space */
k_spin_unlock(&pipe->lock, key);
goto exit;
} else if (unlikely(pipe_full(pipe))) {
/* Timeout has not elapsed, the pipe is open and not resetting,
* we've been notified of available space, but the notified space
* was consumed by another thread before the calling thread.
*/
k_spin_unlock(&pipe->lock, key);
continue;
}
/* The timeout has not elapsed, we've been notified of
* available space, and the pipe is not full. Continue writing.
*/
break;
}
rc = ring_buf_put(&pipe->buf, &data[written], len - written);
if (likely(rc != 0)) {
if (pipe_empty(pipe)) {
notify_waiter(&pipe->data);
#ifdef CONFIG_POLL
z_handle_obj_poll_events(&pipe->poll_events,
K_POLL_STATE_PIPE_DATA_AVAILABLE);
K_POLL_STATE_PIPE_DATA_AVAILABLE);
#endif /* CONFIG_POLL */
}
k_spin_unlock(&pipe->lock, key);
written += rc;
written += ring_buf_put(&pipe->buf, &data[written], len - written);
if (likely(written == len)) {
rc = written;
break;
}
rc = wait_for(&pipe->space, pipe, &key, end);
if (rc != 0) {
if (rc == -EAGAIN) {
rc = written ? written : -EAGAIN;
}
break;
}
}
rc = written;
exit:
SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_pipe, write, pipe, rc);
k_spin_unlock(&pipe->lock, key);
return rc;
}
@ -154,56 +141,43 @@ int z_impl_k_pipe_read(struct k_pipe *pipe, uint8_t *data, size_t len, k_timeout
{
int rc;
size_t read = 0;
k_spinlock_key_t key;
k_timepoint_t end = sys_timepoint_calc(timeout);
k_spinlock_key_t key = k_spin_lock(&pipe->lock);
SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_pipe, read, pipe, data, len, timeout);
while (read < len) {
key = k_spin_lock(&pipe->lock);
if (unlikely(pipe_resetting(pipe))) {
k_spin_unlock(&pipe->lock, key);
rc = -ECANCELED;
goto exit;
} else if (pipe_empty(pipe) && !pipe_closed(pipe)) {
rc = wait_for(&pipe->data, pipe, &key, end);
if (rc == -EAGAIN) {
/* The timeout elapsed */
k_spin_unlock(&pipe->lock, key);
rc = read ? read : -EAGAIN;
goto exit;
} else if (unlikely(rc == -ECANCELED)) {
/* The pipe is being rested. */
k_spin_unlock(&pipe->lock, key);
goto exit;
} else if (unlikely(rc == 0 && pipe_empty(pipe))) {
/* Timeout has not elapsed, we've been notified of available bytes
* but they have been consumed by another thread before the calling
* thread.
*/
k_spin_unlock(&pipe->lock, key);
continue;
}
/* The timeout has not elapsed, we've been notified of
* available bytes, and the pipe is not empty. Continue reading.
*/
}
if (unlikely(pipe_closed(pipe) && pipe_empty(pipe))) {
k_spin_unlock(&pipe->lock, key);
rc = read ? read : -EPIPE;
goto exit;
}
if (unlikely(pipe_resetting(pipe))) {
rc = -ECANCELED;
goto exit;
}
rc = ring_buf_get(&pipe->buf, &data[read], len - read);
if (likely(rc != 0)) {
for (;;) {
if (pipe_full(pipe)) {
notify_waiter(&pipe->space);
}
read += rc;
k_spin_unlock(&pipe->lock, key);
read += ring_buf_get(&pipe->buf, &data[read], len - read);
if (likely(read == len)) {
rc = read;
break;
}
if (unlikely(pipe_closed(pipe))) {
rc = read ? read : -EPIPE;
break;
}
rc = wait_for(&pipe->data, pipe, &key, end);
if (rc != 0) {
if (rc == -EAGAIN) {
rc = read ? read : -EAGAIN;
}
break;
}
}
rc = read;
exit:
SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_pipe, read, pipe, rc);
k_spin_unlock(&pipe->lock, key);
return rc;
}