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fix(util): protect std::condition_variable methods from pthread_cancel

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The changes in GCC 11.x made `std::condition_variable` implementation
internals `noexcept`. `noexcept` is known to interact particularly bad
with `pthread_cancel`, i.e. `__cxxabiv1::__force_unwind` passing through
the `noexcept` call stack frame causes a `std::terminate` call and
immediate termination of the program

Digging through the GCC ML archives[1] lead me to the idea of patching
this with a few pthread_setcancelstate's. As bad as the solution is, it
seems to be the best we can do within C++17 limits and without major
rework.

[1]: https://gcc.gnu.org/legacy-ml/gcc/2017-08/msg00156.html
This commit is contained in:
Aleksei Bavshin
2021-06-04 20:22:16 -07:00
parent 20160749e7
commit 5da268077c
1 changed files with 18 additions and 2 deletions
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20
include/util/sleeper_thread.hpp
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@@ -8,6 +8,20 @@
namespace waybar::util {
/**
* Defer pthread_cancel until the end of a current scope.
*
* Required to protect a scope where it's unsafe to raise `__forced_unwind` exception.
* An example of these is a call of a method marked as `noexcept`; an attempt to cancel within such
* a method may result in a `std::terminate` call.
*/
class CancellationGuard {
int oldstate;
public:
CancellationGuard() { pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate); }
~CancellationGuard() { pthread_setcancelstate(oldstate, &oldstate); }
};
class SleeperThread {
public:
SleeperThread() = default;
@@ -33,14 +47,16 @@ class SleeperThread {
bool isRunning() const { return do_run_; }
auto sleep_for(std::chrono::system_clock::duration dur) {
std::unique_lock lk(mutex_);
std::unique_lock lk(mutex_);
CancellationGuard cancel_lock;
return condvar_.wait_for(lk, dur, [this] { return signal_ || !do_run_; });
}
auto sleep_until(
std::chrono::time_point<std::chrono::system_clock, std::chrono::system_clock::duration>
time_point) {
std::unique_lock lk(mutex_);
std::unique_lock lk(mutex_);
CancellationGuard cancel_lock;
return condvar_.wait_until(lk, time_point, [this] { return signal_ || !do_run_; });
}