This patch adds compatibility code so that we can use signalfd() within QEMU.
signalfd() provides a mechanism to receive signal notification through a
file descriptor. This is very useful in eliminating the signal/select race
condition.
If signalfd() isn't available, we spawn a thread that uses sigwaitinfo() to
emulate it.
Signed-off-by: Anthony Liguori <[EMAIL PROTECTED]>
diff --git a/qemu/kvm-compatfd.c b/qemu/kvm-compatfd.c
index 1b030ba..b1311e2 100644
--- a/qemu/kvm-compatfd.c
+++ b/qemu/kvm-compatfd.c
@@ -15,6 +15,97 @@
#include "qemu-kvm.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;
+
+ sigprocmask(SIG_BLOCK, &info->mask, NULL);
+
+ do {
+ siginfo_t siginfo;
+
+ err = sigwaitinfo(&info->mask, &siginfo);
+ if (err == -1 && errno == EINTR)
+ 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 kvm_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;
+ }
+
+ 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 kvm_signalfd(const sigset_t *mask)
+{
+#if defined(SYS_signalfd)
+ int ret;
+
+ ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
+ if (!(ret == -1 && errno == ENOSYS))
+ return ret;
+#endif
+
+ return kvm_signalfd_compat(mask);
+}
int kvm_eventfd(int *fds)
{
diff --git a/qemu/qemu-kvm.h b/qemu/qemu-kvm.h
index 8fa3c1b..a0dd4a8 100644
--- a/qemu/qemu-kvm.h
+++ b/qemu/qemu-kvm.h
@@ -10,6 +10,8 @@
#include "cpu.h"
+#include <signal.h>
+
int kvm_main_loop(void);
int kvm_qemu_init(void);
int kvm_qemu_create_context(void);
@@ -79,6 +81,16 @@ int handle_powerpc_dcr_read(int vcpu, uint32_t dcrn,
uint32_t *data);
int handle_powerpc_dcr_write(int vcpu,uint32_t dcrn, uint32_t data);
#endif
+#if !defined(SYS_signalfd)
+struct signalfd_siginfo {
+ uint32_t ssi_signo;
+ uint8_t pad[124];
+};
+#else
+#include <linux/signalfd.h>
+#endif
+
+int kvm_signalfd(const sigset_t *mask);
int kvm_eventfd(int *fds);
#define ALIGN(x, y) (((x)+(y)-1) & ~((y)-1))
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