From f05b7507aa28c1a320d839d5c65a72210050dc4d Mon Sep 17 00:00:00 2001
From: Arun Raghavan <arun@asymptotic.io>
Date: Thu, 12 Oct 2023 15:42:23 -0400
Subject: [PATCH] [mod_conference] Avoid a race in member->read_impl access
The conference output loop accesses the member's read_impl while
resampling. The output loop also spawns off the input loop thread, which
is where the member->read_impl is actually initialised. This results in
an uncommon race where the output loop sometimes gets an uninitialised
member->read_impl and bails with logs something like this:
2023-10-12 18:19:01.436844 [DEBUG] conference_loop.c:1340 Setup timer soft success interval: 20 samples: 960 from codec L16
2023-10-12 18:19:01.436844 [DEBUG] conference_loop.c:1497 Outbound conference channel answered, setting CFLAG_ANSWERED
2023-10-12 18:19:01.436844 [NOTICE] switch_core_media.c:15852 Activating write resampler
2023-10-12 18:19:01.436844 [DEBUG] switch_core_media.c:16097 Engaging Write Buffer at 1920 bytes to accommodate 0->1920
2023-10-12 18:19:01.436844 [ERR] switch_core_media.c:16112 Write Buffer 0 bytes Failed!
As a solution, we initialise the member->read_impl even before we start
up the input loop, so that this race can never happen.
---
src/mod/applications/mod_conference/conference_loop.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/mod/applications/mod_conference/conference_loop.c b/src/mod/applications/mod_conference/conference_loop.c
index 8f112f5453..f9b7894d0e 100644
--- a/src/mod/applications/mod_conference/conference_loop.c
+++ b/src/mod/applications/mod_conference/conference_loop.c
@@ -1316,15 +1316,15 @@ void conference_loop_output(conference_member_t *member)
uint32_t flush_len;
uint32_t low_count, bytes;
call_list_t *call_list, *cp;
- switch_codec_implementation_t read_impl = { 0 }, real_read_impl = { 0 };
+ switch_codec_implementation_t real_read_impl = { 0 };
int sanity;
- switch_core_session_get_read_impl(member->session, &read_impl);
+ switch_core_session_get_read_impl(member->session, &member->read_impl);
switch_core_session_get_real_read_impl(member->session, &real_read_impl);
channel = switch_core_session_get_channel(member->session);
- interval = read_impl.microseconds_per_packet / 1000;
+ interval = member->read_impl.microseconds_per_packet / 1000;
samples = switch_samples_per_packet(member->conference->rate, interval);
//csamples = samples;
tsamples = real_read_impl.samples_per_packet;