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net: buf: Disallow blocking allocation in syswq

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Work items on the syswq should always run-to-completion.

Override the timeout value to always be K_NO_WAIT.

Allocating with K_FOREVER leads to deadlocks if the freeing also happens
from the syswq. Non-zero timeouts are also not nice for the other users
of the syswq.

Signed-off-by: Jonathan Rico <jonathan.rico@nordicsemi.no>
This commit is contained in:
Jonathan Rico 2024-04-19 13:09:37 +02:00 committed by Anas Nashif
parent b29dff09fa
commit b08b1c21a0
2 changed files with 33 additions and 12 deletions
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39
include/zephyr/net/buf.h
View file

@ -1315,14 +1315,19 @@ int net_buf_id(struct net_buf *buf);
/** /**
* @brief Allocate a new fixed buffer from a pool. * @brief Allocate a new fixed buffer from a pool.
* *
* @note Some types of data allocators do not support
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
*
* @note The timeout value will be overridden to K_NO_WAIT if called from the
* system workqueue.
*
* @param pool Which pool to allocate the buffer from. * @param pool Which pool to allocate the buffer from.
* @param timeout Affects the action taken should the pool be empty. * @param timeout Affects the action taken should the pool be empty.
* If K_NO_WAIT, then return immediately. If K_FOREVER, then * If K_NO_WAIT, then return immediately. If K_FOREVER, then
* wait as long as necessary. Otherwise, wait until the specified * wait as long as necessary. Otherwise, wait until the specified
* timeout. Note that some types of data allocators do not support * timeout.
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
* *
* @return New buffer or NULL if out of buffers. * @return New buffer or NULL if out of buffers.
*/ */
@ -1350,15 +1355,20 @@ static inline struct net_buf * __must_check net_buf_alloc(struct net_buf_pool *p
/** /**
* @brief Allocate a new variable length buffer from a pool. * @brief Allocate a new variable length buffer from a pool.
* *
* @note Some types of data allocators do not support
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
*
* @note The timeout value will be overridden to K_NO_WAIT if called from the
* system workqueue.
*
* @param pool Which pool to allocate the buffer from. * @param pool Which pool to allocate the buffer from.
* @param size Amount of data the buffer must be able to fit. * @param size Amount of data the buffer must be able to fit.
* @param timeout Affects the action taken should the pool be empty. * @param timeout Affects the action taken should the pool be empty.
* If K_NO_WAIT, then return immediately. If K_FOREVER, then * If K_NO_WAIT, then return immediately. If K_FOREVER, then
* wait as long as necessary. Otherwise, wait until the specified * wait as long as necessary. Otherwise, wait until the specified
* timeout. Note that some types of data allocators do not support * timeout.
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
* *
* @return New buffer or NULL if out of buffers. * @return New buffer or NULL if out of buffers.
*/ */
@ -1382,16 +1392,21 @@ struct net_buf * __must_check net_buf_alloc_len(struct net_buf_pool *pool,
* Allocate a new buffer from a pool, where the data pointer comes from the * Allocate a new buffer from a pool, where the data pointer comes from the
* user and not from the pool. * user and not from the pool.
* *
* @note Some types of data allocators do not support
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
*
* @note The timeout value will be overridden to K_NO_WAIT if called from the
* system workqueue.
*
* @param pool Which pool to allocate the buffer from. * @param pool Which pool to allocate the buffer from.
* @param data External data pointer * @param data External data pointer
* @param size Amount of data the pointed data buffer if able to fit. * @param size Amount of data the pointed data buffer if able to fit.
* @param timeout Affects the action taken should the pool be empty. * @param timeout Affects the action taken should the pool be empty.
* If K_NO_WAIT, then return immediately. If K_FOREVER, then * If K_NO_WAIT, then return immediately. If K_FOREVER, then
* wait as long as necessary. Otherwise, wait until the specified * wait as long as necessary. Otherwise, wait until the specified
* timeout. Note that some types of data allocators do not support * timeout.
* blocking (such as the HEAP type). In this case it's still possible
* for net_buf_alloc() to fail (return NULL) even if it was given
* K_FOREVER.
* *
* @return New buffer or NULL if out of buffers. * @return New buffer or NULL if out of buffers.
*/ */

6
subsys/net/buf.c
View file

@ -271,6 +271,12 @@ struct net_buf *net_buf_alloc_len(struct net_buf_pool *pool, size_t size,
k_spin_unlock(&pool->lock, key); k_spin_unlock(&pool->lock, key);
if (!K_TIMEOUT_EQ(timeout, K_NO_WAIT) &&
k_current_get() == k_work_queue_thread_get(&k_sys_work_q)) {
LOG_DBG("Timeout discarded. No blocking in syswq");
timeout = K_NO_WAIT;
}
#if defined(CONFIG_NET_BUF_LOG) && (CONFIG_NET_BUF_LOG_LEVEL >= LOG_LEVEL_WRN) #if defined(CONFIG_NET_BUF_LOG) && (CONFIG_NET_BUF_LOG_LEVEL >= LOG_LEVEL_WRN)
if (K_TIMEOUT_EQ(timeout, K_FOREVER)) { if (K_TIMEOUT_EQ(timeout, K_FOREVER)) {
uint32_t ref = k_uptime_get_32(); uint32_t ref = k_uptime_get_32();