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From 23a1f554565c0cb9fade1a8f86ab9a09bf3d04e7 Mon Sep 17 00:00:00 2001
From: Thierry Bultel <thierry.bultel@iot.bzh>
Date: Wed, 26 Dec 2018 10:06:38 +0100
Subject: [PATCH] Fixed the SIGSEGV at PCM close
There is a (still not identified) race condition at PCM
close, producing a SIGSEGV when pthread_cancel is called.
Instead of proposing a trick with pthread_setcancelstate,
this fix introduces a cancellation pipe, on which the io_thread
polls. This guaranties a better, safer, exit path.
Signed-off-by: Thierry Bultel <thierry.bultel@iot.bzh>
---
src/asound/bluealsa-pcm.c | 82 +++++++++++++++++++++++++++++++++++++++++------
1 file changed, 72 insertions(+), 10 deletions(-)
diff --git a/src/asound/bluealsa-pcm.c b/src/asound/bluealsa-pcm.c
index 2136964..013aebb 100644
--- a/src/asound/bluealsa-pcm.c
+++ b/src/asound/bluealsa-pcm.c
@@ -67,6 +67,8 @@ struct bluealsa_pcm {
snd_pcm_uframes_t io_hw_boundary;
snd_pcm_uframes_t io_hw_ptr;
+ int cancelPipe[2];
+
};
@@ -107,7 +109,9 @@ static void *io_thread(void *arg) {
struct asrsync asrs;
asrsync_init(&asrs, io->rate);
- debug("Starting IO loop");
+ const char * type = io->stream== SND_PCM_STREAM_CAPTURE?"CAPTURE":"PLAYBACK";
+
+ debug("------------ Starting IO loop (%s)-----------------------", type);
for (;;) {
int tmp;
@@ -124,6 +128,11 @@ static void *io_thread(void *arg) {
debug("IO thread resumed: %d", io->state);
}
+ if (pcm->io_started == false) {
+ debug("io_thread not started -> exit");
+ goto final;
+ }
+
snd_pcm_uframes_t io_ptr = pcm->io_ptr;
snd_pcm_uframes_t io_buffer_size = io->buffer_size;
snd_pcm_uframes_t io_hw_ptr = pcm->io_hw_ptr;
@@ -152,21 +161,44 @@ static void *io_thread(void *arg) {
if (io_hw_ptr >= io_hw_boundary)
io_hw_ptr -= io_hw_boundary;
+ struct pollfd fds[2];
+
+ fds[0].fd = pcm->pcm_fd;
+ fds[1].fd = pcm->cancelPipe[0];
+
+ if (io->stream == SND_PCM_STREAM_CAPTURE)
+ fds[0].events |= POLLIN;
+ else
+ fds[0].events |= POLLOUT;
+
+ fds[1].events = POLLIN | POLLHUP;
+
if (io->stream == SND_PCM_STREAM_CAPTURE) {
/* Read the whole period "atomically". This will assure, that frames
* are not fragmented, so the pointer can be correctly updated. */
- while (len != 0 && (ret = read(pcm->pcm_fd, head, len)) != 0) {
+ while (len != 0 &&
+ pcm->io_started) {
+
+ int pollres = poll(fds, 2, -1);
+
+ if ((fds[1].revents & POLLIN) != 0) {
+ debug("io_thread: CANCELLED");
+ goto final;
+ }
+
+ ret = read(pcm->pcm_fd, head, len);
if (ret == -1) {
- if (errno == EINTR)
- continue;
+ if (errno == EINTR) {
+ break;
+ }
SNDERR("PCM FIFO read error: %s", strerror(errno));
goto final;
}
head += ret;
len -= ret;
- }
+ }
if (ret == 0)
goto final;
@@ -182,9 +214,18 @@ static void *io_thread(void *arg) {
/* Perform atomic write - see the explanation above. */
do {
+
+ int pollres = poll(fds, 2, -1);
+
+ if ((fds[1].revents & POLLIN) != 0) {
+ debug("io_thread: CANCELLED");
+ goto final;
+ }
+
if ((ret = write(pcm->pcm_fd, head, len)) == -1) {
- if (errno == EINTR)
- continue;
+ if (errno == EINTR) {
+ break;
+ }
SNDERR("PCM FIFO write error: %s", strerror(errno));
goto final;
}
@@ -251,12 +292,24 @@ static int bluealsa_start(snd_pcm_ioplug_t *io) {
static int bluealsa_stop(snd_pcm_ioplug_t *io) {
struct bluealsa_pcm *pcm = io->private_data;
- debug("Stopping");
+ debug("Stopping %p", pcm);
+ if (!pcm) {
+ debug("PCM ALREADY CLOSED !");
+ return 0;
+ }
if (pcm->io_started) {
pcm->io_started = false;
- pthread_cancel(pcm->io_thread);
+
+ char dummy = 0;
+
+ if (write(pcm->cancelPipe[1], &dummy, sizeof(dummy)) < 0)
+ debug("Failed to write to the cancellation pipe");
+
pthread_join(pcm->io_thread, NULL);
}
+done:
+ debug("Stop done");
+
return 0;
}
@@ -269,10 +322,14 @@ static snd_pcm_sframes_t bluealsa_pointer(snd_pcm_ioplug_t *io) {
static int bluealsa_close(snd_pcm_ioplug_t *io) {
struct bluealsa_pcm *pcm = io->private_data;
- debug("Closing plugin");
+ debug("Closing plugin %p", pcm);
close(pcm->fd);
close(pcm->event_fd);
+ close(pcm->cancelPipe[0]);
+ close(pcm->cancelPipe[1]);
free(pcm);
+ io->private_data = NULL;
+ debug("PCM closed");
return 0;
}
@@ -649,6 +706,11 @@ SND_PCM_PLUGIN_DEFINE_FUNC(bluealsa) {
pcm->pcm_fd = -1;
pcm->delay_ex = delay;
+ if (pipe(pcm->cancelPipe) == -1) {
+ SNDERR("BlueALSA failed to create cancellation pipe: %s", strerror(errno));
+ ret = -errno;
+ }
+
if ((pcm->fd = bluealsa_open(interface)) == -1) {
SNDERR("BlueALSA connection failed: %s", strerror(errno));
ret = -errno;
--
2.16.4
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