alsactl: use signalfd to catch UNIX signal

In a mode of 'monitor, event loop runs to dispatch asynchronous event
emitted by control node. In this case, UNIX signal is used to terminate
the event loop.

This commit uses signalfd to catch the UNIX signal.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/alsactl/monitor.c b/alsactl/monitor.c
index a3c3ea42ec99d0d8e7c71a1a750c4c5dc475fc56..282fb1caff86d1c20a19c126ba25643f2e41a7e6 100644 (file)
--- a/alsactl/monitor.c
+++ b/alsactl/monitor.c
@@ -26,6 +26,8 @@
 #include <sys/inotify.h>
 #include <limits.h>
 #include <time.h>
+#include <signal.h>
+#include <sys/signalfd.h>
 #include <alsa/asoundlib.h>
 
 #include <stddef.h>
@@ -290,12 +292,18 @@ end:
        return err;
 }
 
-static int prepare_dispatcher(int epfd, int infd, struct list_head *srcs)
+static int prepare_dispatcher(int epfd, int sigfd, int infd,
+                             struct list_head *srcs)
 {
        struct epoll_event ev = {0};
        struct src_entry *entry;
        int err = 0;
 
+       ev.events = EPOLLIN;
+       ev.data.fd = sigfd;
+       if (epoll_ctl(epfd, EPOLL_CTL_ADD, sigfd, &ev) < 0)
+               return -errno;
+
        ev.events = EPOLLIN;
        ev.data.fd = infd;
        if (epoll_ctl(epfd, EPOLL_CTL_ADD, infd, &ev) < 0)
@@ -312,7 +320,7 @@ static int prepare_dispatcher(int epfd, int infd, struct list_head *srcs)
        return err;
 }
 
-static int run_dispatcher(int epfd, int infd, struct list_head *srcs,
+static int run_dispatcher(int epfd, int sigfd, int infd, struct list_head *srcs,
                          bool *retry)
 {
        struct src_entry *entry;
@@ -343,6 +351,9 @@ static int run_dispatcher(int epfd, int infd, struct list_head *srcs,
                for (i = 0; i < count; ++i) {
                        struct epoll_event *ev = epev + i;
 
+                       if (ev->data.fd == sigfd)
+                               goto end;
+
                        if (ev->data.fd == infd) {
                                err = check_control_cdev(infd, retry);
                                if (err < 0 || *retry)
@@ -366,7 +377,8 @@ end:
        return err;
 }
 
-static void clear_dispatcher(int epfd, int infd, struct list_head *srcs)
+static void clear_dispatcher(int epfd, int sigfd, int infd,
+                            struct list_head *srcs)
 {
        struct src_entry *entry;
 
@@ -374,20 +386,49 @@ static void clear_dispatcher(int epfd, int infd, struct list_head *srcs)
                operate_dispatcher(epfd, EPOLL_CTL_DEL, NULL, entry);
 
        epoll_ctl(epfd, EPOLL_CTL_DEL, infd, NULL);
+
+       epoll_ctl(epfd, EPOLL_CTL_DEL, sigfd, NULL);
+}
+
+static int prepare_signalfd(int *sigfd)
+{
+       sigset_t mask;
+       int fd;
+
+       sigemptyset(&mask);
+       sigaddset(&mask, SIGINT);
+       sigaddset(&mask, SIGTERM);
+
+       if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0)
+               return -errno;
+
+       fd = signalfd(-1, &mask, 0);
+       if (fd < 0)
+               return -errno;
+       *sigfd = fd;
+
+       return 0;
 }
 
 int monitor(const char *name)
 {
        LIST_HEAD(srcs);
+       int sigfd = 0;
        int epfd;
        int infd;
        int wd = 0;
        bool retry;
        int err = 0;
 
+       err = prepare_signalfd(&sigfd);
+       if (err < 0)
+               return err;
+
        epfd = epoll_create(1);
-       if (epfd < 0)
+       if (epfd < 0) {
+               close(sigfd);
                return -errno;
+       }
 
        infd = inotify_init1(IN_NONBLOCK);
        if (infd < 0) {
@@ -405,10 +446,10 @@ retry:
        if (err < 0)
                goto error;
 
-       err = prepare_dispatcher(epfd, infd, &srcs);
+       err = prepare_dispatcher(epfd, sigfd, infd, &srcs);
        if (err >= 0)
-               err = run_dispatcher(epfd, infd, &srcs, &retry);
-       clear_dispatcher(epfd, infd, &srcs);
+               err = run_dispatcher(epfd, sigfd, infd, &srcs, &retry);
+       clear_dispatcher(epfd, sigfd, infd, &srcs);
 
        if (retry) {
                // A simple makeshift for timing gap between creation of nodes
@@ -426,5 +467,7 @@ error:
 
        close(epfd);
 
+       close(sigfd);
+
        return err;
 }