Introduce read-write-update locks and guards to prevent deadlocks

This converts t_rwmutex and t_rwmutex_guard into a read-write-update[*]
lock and guard, in an attempt to circumvent the various deadlocks that
were introduced with the addition of lines_mtx in 38bb6b7.

[*] For more details, see https://stackoverflow.com/a/18785300 and
http://lkml.iu.edu/hypermail/linux/kernel/0004.3/0117.html.

Note that this is not a real fix; this would require analyzing and
refactoring phone.cpp, which is well beyond my abilities.  This is at
best a workaround that appears to conveniently dodge all the deadlocks
I've encountered so far.

(It would have been more proper to introduce a separate class for this
purpose, but this would have required modifying over 80 lines just to
change one type for another.  As phone_users_mtx is the only other
instance of this class, the impact of subverting t_rwmutex directly is
minimal.)

1 files changed, 1 insertions, 0 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 01f4997..0770bce 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -81,6 +81,7 @@ add_executable(twinkle-console
 )
 
 set(twinkle_LIBS
+	-latomic
 	-lpthread
 	-lresolv
 	${LibMagic_LIBRARY}