[patch uq/master 1/8] signalfd compatibility

Marcelo Tosatti
2010-10-06T17:39:56Z

[-- Attachment #1: signalfd --]
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Port qemu-kvm's signalfd compat code.

commit 5a7fdd0abd7cd24dac205317a4195446ab8748b5
Author: Anthony Liguori <aliguori@us.ibm.com>
Date: Wed May 7 11:55:47 2008 -0500

Use signalfd() in io-thread

This patch reworks the IO thread to use signalfd() instead of sigtimedwait()
This will eliminate the need to use SIGIO everywhere.

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

Index: qemu/compatfd.c
===================================================================
--- /dev/null
+++ qemu/compatfd.c
@@ -0,0 +1,117 @@
+/*
+ * signalfd/eventfd compatibility
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ * Anthony Liguori <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "compatfd.h"
+
+#include <sys/syscall.h>
+#include <pthread.h>
+
+struct sigfd_compat_info
+{
+ sigset_t mask;
+ int fd;
+};
+
+static void *sigwait_compat(void *opaque)
+{
+ struct sigfd_compat_info *info = opaque;
+ int err;
+ sigset_t all;
+
+ sigfillset(&all);
+ sigprocmask(SIG_BLOCK, &all, NULL);
+
+ do {
+ siginfo_t siginfo;
+
+ err = sigwaitinfo(&info->mask, &siginfo);
+ if (err == -1 && errno == EINTR) {
+ err = 0;
+ continue;
+ }
+
+ if (err > 0) {
+ char buffer[128];
+ size_t offset = 0;
+
+ memcpy(buffer, &err, sizeof(err));
+ while (offset < sizeof(buffer)) {
+ ssize_t len;
+
+ len = write(info->fd, buffer + offset,
+ sizeof(buffer) - offset);
+ if (len == -1 && errno == EINTR)
+ continue;
+
+ if (len <= 0) {
+ err = -1;
+ break;
+ }
+
+ offset += len;
+ }
+ }
+ } while (err >= 0);
+
+ return NULL;
+}
+
+static int qemu_signalfd_compat(const sigset_t *mask)
+{
+ pthread_attr_t attr;
+ pthread_t tid;
+ struct sigfd_compat_info *info;
+ int fds[2];
+
+ info = malloc(sizeof(*info));
+ if (info == NULL) {
+ errno = ENOMEM;
+ return -1;
+ }
+
+ if (pipe(fds) == -1) {
+ free(info);
+ return -1;
+ }
+
+ qemu_set_cloexec(fds[0]);
+ qemu_set_cloexec(fds[1]);
+
+ memcpy(&info->mask, mask, sizeof(*mask));
+ info->fd = fds[1];
+
+ pthread_attr_init(&attr);
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+
+ pthread_create(&tid, &attr, sigwait_compat, info);
+
+ pthread_attr_destroy(&attr);
+
+ return fds[0];
+}
+
+int qemu_signalfd(const sigset_t *mask)
+{
+#if defined(CONFIG_SIGNALFD)
+ int ret;
+
+ ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
+ if (ret != -1) {
+ qemu_set_cloexec(ret);
+ return ret;
+ }
+#endif
+
+ return qemu_signalfd_compat(mask);
+}
Index: qemu/compatfd.h
===================================================================
--- /dev/null
+++ qemu/compatfd.h
@@ -0,0 +1,43 @@
+/*
+ * signalfd/eventfd compatibility
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ * Anthony Liguori <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_COMPATFD_H
+#define QEMU_COMPATFD_H
+
+#include <signal.h>
+
+struct qemu_signalfd_siginfo {
+ uint32_t ssi_signo; /* Signal number */
+ int32_t ssi_errno; /* Error number (unused) */
+ int32_t ssi_code; /* Signal code */
+ uint32_t ssi_pid; /* PID of sender */
+ uint32_t ssi_uid; /* Real UID of sender */
+ int32_t ssi_fd; /* File descriptor (SIGIO) */
+ uint32_t ssi_tid; /* Kernel timer ID (POSIX timers) */
+ uint32_t ssi_band; /* Band event (SIGIO) */
+ uint32_t ssi_overrun; /* POSIX timer overrun count */
+ uint32_t ssi_trapno; /* Trap number that caused signal */
+ int32_t ssi_status; /* Exit status or signal (SIGCHLD) */
+ int32_t ssi_int; /* Integer sent by sigqueue(2) */
+ uint64_t ssi_ptr; /* Pointer sent by sigqueue(2) */
+ uint64_t ssi_utime; /* User CPU time consumed (SIGCHLD) */
+ uint64_t ssi_stime; /* System CPU time consumed (SIGCHLD) */
+ uint64_t ssi_addr; /* Address that generated signal
+ (for hardware-generated signals) */
+ uint8_t pad[48]; /* Pad size to 128 bytes (allow for
+ additional fields in the future) */
+};
+
+int qemu_signalfd(const sigset_t *mask);
+
+#endif
Index: qemu/Makefile.objs
===================================================================
--- qemu.orig/Makefile.objs
+++ qemu/Makefile.objs
@@ -121,6 +121,7 @@ common-obj-y += $(addprefix ui/, $(ui-ob

common-obj-y += iov.o acl.o
common-obj-$(CONFIG_THREAD) += qemu-thread.o
+common-obj-$(CONFIG_IOTHREAD) += compatfd.o
common-obj-y += notify.o event_notifier.o
common-obj-y += qemu-timer.o

Index: qemu/configure
===================================================================
--- qemu.orig/configure
+++ qemu/configure
@@ -1936,6 +1936,21 @@ if compile_prog "" "" ; then
splice=yes
fi

+##########################################
+# signalfd probe
+signalfd="no"
+cat > $TMPC << EOF
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <signal.h>
+int main(void) { return syscall(SYS_signalfd, -1, NULL, _NSIG / 8); }
+EOF
+
+if compile_prog "" "" ; then
+ signalfd=yes
+fi
+
# check if eventfd is supported
eventfd=no
cat > $TMPC << EOF
@@ -2509,6 +2524,9 @@ fi
if test "$fdt" = "yes" ; then
echo "CONFIG_FDT=y" >> $config_host_mak
fi
+if test "$signalfd" = "yes" ; then
+ echo "CONFIG_SIGNALFD=y" >> $config_host_mak
+fi
if test "$need_offsetof" = "yes" ; then
echo "CONFIG_NEED_OFFSETOF=y" >> $config_host_mak
fi