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[socket] Release LWIP lock during SO_RCVTIMEO wait and handle spurious wakes

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- Extract read_locked_() to avoid holding LWIP_LOCK during socket_delay(),
  which would block recv_fn() on RP2040 (needs async_context lock)
- Loop around socket_delay() for remaining time on spurious wakes from
  other sockets, ensuring SO_RCVTIMEO semantics are correct
- Fix readv() to use read_locked_() directly instead of calling read(),
  avoiding recursive locking and unintended socket_delay() waits
This commit is contained in:
J. Nick Koston
2026-03-11 21:19:51 -10:00
parent 381ae03db9
commit 96f59a11ac
2 changed files with 41 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
esphome/components/socket/lwip_raw_tcp_impl.cpp
+40 -21
View File
@@ -516,36 +516,42 @@ err_t LWIPRawImpl::recv_fn(struct pbuf *pb, err_t err) {
}
ssize_t LWIPRawImpl::read(void *buf, size_t len) {
// If SO_RCVTIMEO is set and no data available, wait without holding lock.
// These reads are safe unlocked (atomic pointer/bool on ARM/Xtensa) —
// they're just hints; the authoritative check happens under LWIP_LOCK below.
// Lock must not be held during socket_delay() so recv_fn() can run on RP2040.
if (this->recv_timeout_cs_ > 0 && this->rx_buf_ == nullptr && !this->rx_closed_ && this->pcb_ != nullptr) {
// Loop until data arrives, connection closes, or the full timeout elapses.
// socket_delay() may return early due to other sockets waking the global
// socket_wake() flag, so we re-enter for the remaining time.
uint32_t timeout_ms = this->recv_timeout_cs_ * 10;
uint32_t start = millis();
while (this->rx_buf_ == nullptr && !this->rx_closed_ && this->pcb_ != nullptr) {
uint32_t elapsed = millis() - start;
if (elapsed >= timeout_ms)
break;
socket_delay(timeout_ms - elapsed);
}
}
LWIP_LOCK();
if (this->pcb_ == nullptr) {
errno = ECONNRESET;
return -1;
}
if (this->rx_closed_ && this->rx_buf_ == nullptr) {
if (this->rx_closed_ && this->rx_buf_ == nullptr)
return 0;
}
if (len == 0) {
if (len == 0)
return 0;
}
if (this->rx_buf_ == nullptr) {
if (this->recv_timeout_cs_ > 0) {
// Wait efficiently for data — socket_delay() sleeps and wakes
// immediately when recv_fn() fires (data arrives via socket_wake())
socket_delay(this->recv_timeout_cs_ * 10);
// Recheck after waking — data or close may have arrived
if (this->rx_closed_ && this->rx_buf_ == nullptr)
return 0;
if (this->rx_buf_ == nullptr) {
errno = EWOULDBLOCK;
return -1;
}
// Data arrived, fall through to copy
} else {
errno = EWOULDBLOCK;
return -1;
}
errno = EWOULDBLOCK;
return -1;
}
return this->read_locked_(buf, len);
}
ssize_t LWIPRawImpl::read_locked_(void *buf, size_t len) {
// Caller must hold LWIP_LOCK and ensure rx_buf_ != nullptr
size_t read = 0;
uint8_t *buf8 = reinterpret_cast<uint8_t *>(buf);
while (len && this->rx_buf_ != nullptr) {
@@ -591,9 +597,22 @@ ssize_t LWIPRawImpl::read(void *buf, size_t len) {
ssize_t LWIPRawImpl::readv(const struct iovec *iov, int iovcnt) {
LWIP_LOCK(); // Hold for entire scatter-gather operation
if (this->pcb_ == nullptr) {
errno = ECONNRESET;
return -1;
}
if (this->rx_closed_ && this->rx_buf_ == nullptr) {
return 0;
}
ssize_t ret = 0;
for (int i = 0; i < iovcnt; i++) {
ssize_t err = this->read(reinterpret_cast<uint8_t *>(iov[i].iov_base), iov[i].iov_len);
if (this->rx_buf_ == nullptr) {
if (ret != 0)
break;
errno = EWOULDBLOCK;
return -1;
}
ssize_t err = this->read_locked_(reinterpret_cast<uint8_t *>(iov[i].iov_base), iov[i].iov_len);
if (err == -1) {
if (ret != 0) {
// if we already read some don't return an error
esphome/components/socket/lwip_raw_tcp_impl.h
+1
View File
@@ -120,6 +120,7 @@ class LWIPRawImpl : public LWIPRawCommon {
static err_t s_recv_fn(void *arg, struct tcp_pcb *pcb, struct pbuf *pb, err_t err);
protected:
ssize_t read_locked_(void *buf, size_t len);
ssize_t internal_write_(const void *buf, size_t len);
int internal_output_();