From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: [patch 2/2] qemu-kvm: drop posix-aio-compat.cs signalfd usage
Date: Mon, 06 Sep 2010 17:20:17 -0300
Message-ID: <20100906202301.361862359@amt.cnet>
References: <20100906202015.433641568@amt.cnet>
Cc: avi@redhat.com, Anthony Liguori <anthony@codemonkey.ws>,
	Marcelo Tosatti <mtosatti@redhat.com>
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
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Content-Disposition: inline; filename=posix-aio-compat-use-signal
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Block SIGUSR2, which makes the signal be handled through qemu-kvm.c's
signalfd.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: qemu-kvm/posix-aio-compat.c
===================================================================
--- qemu-kvm.orig/posix-aio-compat.c
+++ qemu-kvm/posix-aio-compat.c
@@ -26,7 +26,6 @@
 #include "osdep.h"
 #include "qemu-common.h"
 #include "block_int.h"
-#include "compatfd.h"
 
 #include "block/raw-posix-aio.h"
 
@@ -54,7 +53,7 @@ struct qemu_paiocb {
 };
 
 typedef struct PosixAioState {
-    int fd;
+    int rfd, wfd;
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
@@ -473,29 +472,18 @@ static int posix_aio_process_queue(void 
 static void posix_aio_read(void *opaque)
 {
     PosixAioState *s = opaque;
-    union {
-        struct qemu_signalfd_siginfo siginfo;
-        char buf[128];
-    } sig;
-    size_t offset;
-
-    /* try to read from signalfd, don't freak out if we can't read anything */
-    offset = 0;
-    while (offset < 128) {
-        ssize_t len;
+    ssize_t len;
 
-        len = read(s->fd, sig.buf + offset, 128 - offset);
-        if (len == -1 && errno == EINTR)
-            continue;
-        if (len == -1 && errno == EAGAIN) {
-            /* there is no natural reason for this to happen,
-             * so we'll spin hard until we get everything just
-             * to be on the safe side. */
-            if (offset > 0)
-                continue;
-        }
+    /* read all bytes from signal pipe */
+    for (;;) {
+        char bytes[16];
 
-        offset += len;
+        len = read(s->rfd, bytes, sizeof(bytes));
+        if (len == -1 && errno == EINTR)
+            continue; /* try again */
+        if (len == sizeof(bytes))
+            continue; /* more to read */
+        break;
     }
 
     posix_aio_process_queue(s);
@@ -509,6 +497,20 @@ static int posix_aio_flush(void *opaque)
 
 static PosixAioState *posix_aio_state;
 
+static void aio_signal_handler(int signum)
+{
+    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()");
+    }
+
+    qemu_service_io();
+}
+
 static void paio_remove(struct qemu_paiocb *acb)
 {
     struct qemu_paiocb **pacb;
@@ -610,8 +612,9 @@ BlockDriverAIOCB *paio_ioctl(BlockDriver
 
 int paio_init(void)
 {
-    sigset_t mask;
+    struct sigaction act;
     PosixAioState *s;
+    int fds[2];
     int ret;
 
     if (posix_aio_state)
@@ -619,21 +622,24 @@ int paio_init(void)
 
     s = qemu_malloc(sizeof(PosixAioState));
 
-    /* Make sure to block AIO signal */
-    sigemptyset(&mask);
-    sigaddset(&mask, SIGUSR2);
-    sigprocmask(SIG_BLOCK, &mask, NULL);
+    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;
-    s->fd = qemu_signalfd(&mask);
-    if (s->fd == -1) {
-        fprintf(stderr, "failed to create signalfd\n");
+    if (qemu_pipe(fds) == -1) {
+        fprintf(stderr, "failed to create pipe\n");
         return -1;
     }
 
-    fcntl(s->fd, F_SETFL, O_NONBLOCK);
+    s->rfd = fds[0];
+    s->wfd = fds[1];
+
+    fcntl(s->rfd, F_SETFL, O_NONBLOCK);
+    fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 
-    qemu_aio_set_fd_handler(s->fd, posix_aio_read, NULL, posix_aio_flush,
+    qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
         posix_aio_process_queue, s);
 
     ret = pthread_attr_init(&attr);
Index: qemu-kvm/qemu-kvm.c
===================================================================
--- qemu-kvm.orig/qemu-kvm.c
+++ qemu-kvm/qemu-kvm.c
@@ -1680,6 +1680,7 @@ int kvm_main_loop(void)
     sigemptyset(&mask);
     sigaddset(&mask, SIGIO);
     sigaddset(&mask, SIGALRM);
+    sigaddset(&mask, SIGUSR2);
     sigaddset(&mask, SIGBUS);
     sigprocmask(SIG_BLOCK, &mask, NULL);