[PATCH v3] pipe-source: optional suspend source when no writers connected to fifo

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Add autosuspend=<bool> option. Enabling this option will make
pipe-source suspended when all writers closed fifo. Source will
be automatically unsuspended if any data will be written to pipe
and suspended again when last writer closed fifo.
---
 src/modules/module-pipe-source.c | 136 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 129 insertions(+), 7 deletions(-)

diff --git a/src/modules/module-pipe-source.c b/src/modules/module-pipe-source.c
index f8284c1..af7badc 100644
--- a/src/modules/module-pipe-source.c
+++ b/src/modules/module-pipe-source.c
@@ -57,11 +57,24 @@ PA_MODULE_USAGE(
         "format=<sample format> "
         "rate=<sample rate> "
         "channels=<number of channels> "
-        "channel_map=<channel map>");
+        "channel_map=<channel map> "
+        "autosuspend=<boolean>");
 
 #define DEFAULT_FILE_NAME "/tmp/music.input"
 #define DEFAULT_SOURCE_NAME "fifo_input"
 
+struct pipe_source_msg {
+    pa_msgobject parent;
+};
+
+typedef struct pipe_source_msg pipe_source_msg;
+PA_DEFINE_PRIVATE_CLASS(pipe_source_msg, pa_msgobject);
+
+enum {
+    PIPE_SOURCE_SUSPEND,
+    PIPE_SOURCE_RESUME,
+};
+
 struct userdata {
     pa_core *core;
     pa_module *module;
@@ -71,7 +84,10 @@ struct userdata {
     pa_thread_mq thread_mq;
     pa_rtpoll *rtpoll;
 
+    pipe_source_msg *msg;
+
     char *filename;
+    int corkfd;
     int fd;
 
     pa_memchunk memchunk;
@@ -87,9 +103,41 @@ static const char* const valid_modargs[] = {
     "rate",
     "channels",
     "channel_map",
+    "autosuspend",
     NULL
 };
 
+/* Called from main context */
+static int pipe_source_process_msg(
+        pa_msgobject *o,
+        int code,
+        void *data,
+        int64_t offset,
+        pa_memchunk *chunk) {
+
+    struct userdata *u = (struct userdata *) data;
+
+    pa_assert(u);
+
+    switch (code) {
+        case PIPE_SOURCE_SUSPEND:
+            pa_log_debug("Suspending source %s because no writers left", u->source->name);
+            pa_source_suspend(u->source, true, PA_SUSPEND_APPLICATION);
+            break;
+
+        case PIPE_SOURCE_RESUME:
+            pa_log_debug("Resuming source %s because writer connected", u->source->name);
+            pa_source_suspend(u->source, false, PA_SUSPEND_APPLICATION);
+            break;
+
+        default:
+            pa_assert_not_reached();
+    }
+
+    return 0;
+}
+
+/* Called from thread context */
 static int source_process_msg(
         pa_msgobject *o,
         int code,
@@ -135,8 +183,15 @@ static void thread_func(void *userdata) {
 
         pollfd = pa_rtpoll_item_get_pollfd(u->rtpoll_item, NULL);
 
+        /* Writer connected */
+        if (u->corkfd >= 0 && pollfd->revents & POLLIN) {
+            pa_asyncmsgq_post(pa_thread_mq_get()->outq, PA_MSGOBJECT(u->msg), PIPE_SOURCE_RESUME, u, 0, NULL, NULL);
+            pa_assert_se(pa_close(u->corkfd) == 0);
+            u->corkfd = -1;
+        }
+
         /* Try to read some data and pass it on to the source driver */
-        if (u->source->thread_info.state == PA_SOURCE_RUNNING && pollfd->revents) {
+        if (u->source->thread_info.state == PA_SOURCE_RUNNING && pollfd->revents & POLLIN) {
             ssize_t l;
             void *p;
 
@@ -151,8 +206,6 @@ static void thread_func(void *userdata) {
             l = pa_read(u->fd, (uint8_t*) p + u->memchunk.index, pa_memblock_get_length(u->memchunk.memblock) - u->memchunk.index, &read_type);
             pa_memblock_release(u->memchunk.memblock);
 
-            pa_assert(l != 0); /* EOF cannot happen, since we opened the fifo for both reading and writing */
-
             if (l < 0) {
 
                 if (errno == EINTR)
@@ -162,6 +215,11 @@ static void thread_func(void *userdata) {
                     goto fail;
                 }
 
+            } else if (l == 0) {
+
+                /* Nothing to read */
+                pollfd->revents = 0;
+
             } else {
 
                 u->memchunk.length = (size_t) l;
@@ -178,7 +236,7 @@ static void thread_func(void *userdata) {
         }
 
         /* Hmm, nothing to do. Let's sleep */
-        pollfd->events = (short) (u->source->thread_info.state == PA_SOURCE_RUNNING ? POLLIN : 0);
+        pollfd->events = (short) ((u->source->thread_info.state == PA_SOURCE_RUNNING || u->corkfd >= 0) ? POLLIN : 0);
 
         if ((ret = pa_rtpoll_run(u->rtpoll)) < 0)
             goto fail;
@@ -188,6 +246,29 @@ static void thread_func(void *userdata) {
 
         pollfd = pa_rtpoll_item_get_pollfd(u->rtpoll_item, NULL);
 
+        /* Last writer disconnected but data may still be in the buffer */
+        if (pollfd->revents & POLLHUP) {
+            int l = 0;
+
+#ifdef FIONREAD
+            ioctl(u->fd, FIONREAD, &l);
+#endif
+
+            if (!l && u->corkfd < 0) {
+                /* Suspend source */
+                pa_asyncmsgq_post(pa_thread_mq_get()->outq, PA_MSGOBJECT(u->msg), PIPE_SOURCE_SUSPEND, u, 0, NULL, NULL);
+
+                /* Open fifo for writing to stop POLLHUP spam */
+                if ((u->corkfd = pa_open_cloexec(u->filename, O_WRONLY, 0)) < 0) {
+                    pa_log("open('%s'): %s", u->filename, pa_cstrerror(errno));
+                    goto fail;
+                }
+            }
+
+            /* Ignore POOLHUP anyway */
+            pollfd->revents &= ~POLLHUP;
+        }
+
         if (pollfd->revents & ~POLLIN) {
             pa_log("FIFO shutdown.");
             goto fail;
@@ -212,6 +293,7 @@ int pa__init(pa_module *m) {
     pa_modargs *ma;
     struct pollfd *pollfd;
     pa_source_new_data data;
+    bool autosuspend = false;
 
     pa_assert(m);
 
@@ -238,17 +320,51 @@ int pa__init(pa_module *m) {
         goto fail;
     }
 
+    u->corkfd = -1;
+
+    if (!(u->msg = pa_msgobject_new(pipe_source_msg)))
+        goto fail;
+
+    u->msg->parent.process_msg = pipe_source_process_msg;
+
     u->filename = pa_runtime_path(pa_modargs_get_value(ma, "file", DEFAULT_FILE_NAME));
 
     if (mkfifo(u->filename, 0666) < 0) {
         pa_log("mkfifo('%s'): %s", u->filename, pa_cstrerror(errno));
         goto fail;
     }
-    if ((u->fd = pa_open_cloexec(u->filename, O_RDWR, 0)) < 0) {
-        pa_log("open('%s'): %s", u->filename, pa_cstrerror(errno));
+
+    if (pa_modargs_get_value_boolean(ma, "autosuspend", &autosuspend) < 0) {
+        pa_log("Failed to parse autosuspend= argument.");
         goto fail;
     }
 
+    if (autosuspend) {
+        int rwfd;
+
+        /* Open fifo for read and write first, so the next open for read-only
+           will be succeded immediately */
+        if ((rwfd = pa_open_cloexec(u->filename, O_RDWR, 0)) < 0) {
+            pa_log("open('%s'): %s", u->filename, pa_cstrerror(errno));
+            goto fail;
+        }
+
+        if ((u->fd = pa_open_cloexec(u->filename, O_RDONLY, 0)) < 0) {
+            pa_log("open('%s'): %s", u->filename, pa_cstrerror(errno));
+            pa_assert_se(pa_close(rwfd) == 0);
+            goto fail;
+        }
+
+        pa_assert_se(pa_close(rwfd) == 0);
+
+    } else {
+        /* Open fifo for read and write, so there will be at least one writer */
+        if ((u->fd = pa_open_cloexec(u->filename, O_RDWR, 0)) < 0) {
+            pa_log("open('%s'): %s", u->filename, pa_cstrerror(errno));
+            goto fail;
+        }
+    }
+
     pa_make_fd_nonblock(u->fd);
 
     if (fstat(u->fd, &st) < 0) {
@@ -360,6 +476,12 @@ void pa__done(pa_module *m) {
         pa_xfree(u->filename);
     }
 
+    if (u->msg)
+        pa_xfree(u->msg);
+
+    if (u->corkfd >= 0)
+        pa_assert_se(pa_close(u->corkfd) == 0);
+
     if (u->fd >= 0)
         pa_assert_se(pa_close(u->fd) == 0);
 
-- 
1.8.3.1



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