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TCP: immediately trigger the service thread to write PDU

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IF qe queue a new PDU to an empty outqueue then the mt service thread
will still be stuck in poll() until it timesout or the socket becomes
readable.

Fix this by sending SIGUSR1 to the service thread when we queue a PDU
to an empty queue. This will break out of poll() and we can immediately
go and write to the socket.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
This commit is contained in:
Ronnie Sahlberg
2025-04-13 10:05:53 +10:00
parent f63ed0b76e
commit 37bc6fcd81
2 changed files with 48 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
lib/multithreading.c
View File

@@ -139,6 +139,9 @@ int iscsi_mt_sem_wait(libiscsi_sem_t* sem)
#elif defined(HAVE_PTHREAD) /* WIN32 */
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/syscall.h>
@@ -156,13 +159,20 @@ iscsi_tid_t iscsi_mt_get_tid(void)
#endif
}
static void on_sigusr1(int _unused)
{
}
static void *iscsi_mt_service_thread(void *arg)
{
struct iscsi_context *iscsi = (struct iscsi_context *)arg;
struct pollfd pfd;
int revents;
int ret;
/* set signal to break poll when we need to send more data */
signal(SIGUSR1, on_sigusr1);
iscsi->multithreading_enabled = 1;
/* TODO: add timeout scanning */
@@ -172,12 +182,21 @@ static void *iscsi_mt_service_thread(void *arg)
pfd.revents = 0;
ret = poll(&pfd, 1, iscsi->poll_timeout);
if (ret < 0) {
if (ret < 0 && errno == EINTR) {
/*
* Got a signal. Assume it is because we need to start writing new PDUs
* to the socket.
*/
revents = POLLOUT;
goto call_service;
}
if (ret < 0) {
iscsi_set_error(iscsi, "Poll failed");
revents = -1;
} else {
revents = pfd.revents;
}
call_service:
if (iscsi_service(iscsi, revents) < 0) {
if (revents != -1)
iscsi_set_error(iscsi, "iscsi_service failed");

32
lib/socket.c
View File

@@ -62,6 +62,10 @@
#include <sys/uio.h>
#endif
#ifdef HAVE_PTHREAD
#include <signal.h>
#endif
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
@@ -88,7 +92,7 @@ union socket_address {
void
iscsi_add_to_outqueue(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
{
struct iscsi_pdu *current = iscsi->outqueue;
struct iscsi_pdu *current;
struct iscsi_pdu *last = NULL;
if (iscsi->scsi_timeout > 0) {
@@ -97,12 +101,15 @@ iscsi_add_to_outqueue(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
pdu->scsi_timeout = 0;
}
if (iscsi->outqueue == NULL) {
iscsi_mt_mutex_lock(&iscsi->iscsi_mutex);
current = iscsi->outqueue;
if (iscsi->outqueue == NULL) {
iscsi->outqueue = pdu;
pdu->next = NULL;
return;
goto finished;
}
/* queue pdus in ascending order of CmdSN.
* ensure that pakets with the same CmdSN are kept in FIFO order.
* immediate PDUs are queued in front of queue with the CmdSN
@@ -131,7 +138,7 @@ iscsi_add_to_outqueue(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
iscsi->outqueue=pdu;
}
pdu->next = current;
return;
goto finished;
}
last=current;
current=current->next;
@@ -139,9 +146,24 @@ iscsi_add_to_outqueue(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
last->next = pdu;
pdu->next = NULL;
finished:
iscsi_mt_mutex_unlock(&iscsi->iscsi_mutex);
/* TODO QQQ need to immediately send for the non multithreading case too
* and for the Windows API too */
#if defined(HAVE_MULTITHREADING) && defined(HAVE_PTHREAD)
if (current == NULL && pdu == iscsi->outqueue) {
if(iscsi->multithreading_enabled) {
pthread_kill(iscsi->service_thread, SIGUSR1);
}
}
#endif
return;
}
void iscsi_decrement_iface_rr() {
/* TODO QQQ use an atomic here */
iface_rr--;
}