[Qemu-devel] [PATCH v2] block: avoid SIGUSR2

[Frediano Ziglio]

Now that iothread is always compiled sending a signal seems only an
additional step. This patch also avoid writing to two pipe (one from signal
and one in qemu_service_io).

Work with kvm enabled or disabled. strace output is more readable (less 
syscalls).

Signed-off-by: Frediano Ziglio <address@hidden>
---
 cpus.c             |    5 -----
 posix-aio-compat.c |   29 +++++++++--------------------
 2 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/cpus.c b/cpus.c
index 54c188c..d0cfe91 100644
--- a/cpus.c
+++ b/cpus.c
@@ -380,11 +380,6 @@ static int qemu_signal_init(void)
     int sigfd;
     sigset_t set;
 
-    /* SIGUSR2 used by posix-aio-compat.c */
-    sigemptyset(&set);
-    sigaddset(&set, SIGUSR2);
-    pthread_sigmask(SIG_UNBLOCK, &set, NULL);
-
     /*
      * SIG_IPI must be blocked in the main thread and must not be caught
      * by sigwait() in the signal thread. Otherwise, the cpu thread will
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 3193dbf..185d5b2 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -42,7 +42,6 @@ struct qemu_paiocb {
     int aio_niov;
     size_t aio_nbytes;
 #define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
-    int ev_signo;
     off_t aio_offset;
 
     QTAILQ_ENTRY(qemu_paiocb) node;
@@ -309,6 +308,8 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
+static void posix_aio_notify_event(void);
+
 static void *aio_thread(void *unused)
 {
     pid_t pid;
@@ -381,7 +382,7 @@ static void *aio_thread(void *unused)
         aiocb->ret = ret;
         mutex_unlock(&lock);
 
-        if (kill(pid, aiocb->ev_signo)) die("kill failed");
+        posix_aio_notify_event();
     }
 
     cur_threads--;
@@ -548,18 +549,14 @@ static int posix_aio_flush(void *opaque)
 
 static PosixAioState *posix_aio_state;
 
-static void aio_signal_handler(int signum)
+static void posix_aio_notify_event(void)
 {
-    if (posix_aio_state) {
-        char byte = 0;
-        ssize_t ret;
-
-        ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
-        if (ret < 0 && errno != EAGAIN)
-            die("write()");
-    }
+    char byte = 0;
+    ssize_t ret;
 
-    qemu_service_io();
+    ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
+    if (ret < 0 && errno != EAGAIN)
+        die("write()");
 }
 
 static void paio_remove(struct qemu_paiocb *acb)
@@ -623,7 +620,6 @@ BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
         return NULL;
     acb->aio_type = type;
     acb->aio_fildes = fd;
-    acb->ev_signo = SIGUSR2;
 
     if (qiov) {
         acb->aio_iov = qiov->iov;
@@ -651,7 +647,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
         return NULL;
     acb->aio_type = QEMU_AIO_IOCTL;
     acb->aio_fildes = fd;
-    acb->ev_signo = SIGUSR2;
     acb->aio_offset = 0;
     acb->aio_ioctl_buf = buf;
     acb->aio_ioctl_cmd = req;
@@ -665,7 +660,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 
 int paio_init(void)
 {
-    struct sigaction act;
     PosixAioState *s;
     int fds[2];
     int ret;
@@ -675,11 +669,6 @@ int paio_init(void)
 
     s = g_malloc(sizeof(PosixAioState));
 
-    sigfillset(&act.sa_mask);
-    act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
-    act.sa_handler = aio_signal_handler;
-    sigaction(SIGUSR2, &act, NULL);
-
     s->first_aio = NULL;
     if (qemu_pipe(fds) == -1) {
         fprintf(stderr, "failed to create pipe\n");
-- 
1.7.1