From b03ecb3d744a6d60d01ff1ace0c01b08eef01307 Mon Sep 17 00:00:00 2001 From: literallyvoid Date: Sat, 12 Apr 2025 17:21:57 -0700 Subject: [PATCH 1/4] Move signal handling to main thread --- src/main.cpp | 130 +++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 105 insertions(+), 25 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index 045b2cd4..94355e1b 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -1,3 +1,4 @@ +#include #include #include #include @@ -7,6 +8,7 @@ #include #include "client.hpp" +#include "util/SafeSignal.hpp" std::mutex reap_mtx; std::list reap; @@ -70,37 +72,115 @@ void startSignalThread() { } } +static int signal_pipe_write_fd; + +// Write a single signal to `signal_pipe_write_fd`. +// This function is set as a signal handler, so it must be async-signal-safe. +static void writeSignalToPipe(int signum) { + ssize_t amt = write(signal_pipe_write_fd, &signum, sizeof(int)); + + // There's not much we can safely do inside of a signal handler. + // Let's just ignore any errors. + (void) amt; +} + +// This initializes `signal_pipe_write_fd`, and sets up signal handlers. +// +// This function will run forever, emitting every `SIGUSR1`, `SIGUSR2`, +// `SIGINT`, and `SIGRTMIN + 1`...`SIGRTMAX` signal received to +// `signal_handler`. +static void catchSignals(waybar::SafeSignal &signal_handler) { + int fd[2]; + pipe(fd); + + int signal_pipe_read_fd = fd[0]; + signal_pipe_write_fd = fd[1]; + + // This pipe should be able to buffer ~thousands of signals. If it fills up, + // we'll drop signals instead of blocking. + + // We can't allow the write end to block because we'll be writing to it in a + // signal handler, which could interrupt the loop that's reading from it and + // deadlock. + + fcntl(signal_pipe_write_fd, F_SETFL, O_NONBLOCK); + + std::signal(SIGUSR1, writeSignalToPipe); + std::signal(SIGUSR2, writeSignalToPipe); + std::signal(SIGINT, writeSignalToPipe); + + for (int sig = SIGRTMIN + 1; sig <= SIGRTMAX; ++sig) { + std::signal(sig, writeSignalToPipe); + } + + while (true) { + int signum; + ssize_t amt = read(signal_pipe_read_fd, &signum, sizeof(int)); + if (amt < 0) { + spdlog::error("read from signal pipe failed with error {}, closing thread", strerror(errno)); + break; + } + + if (amt != sizeof(int)) { + continue; + } + + signal_handler.emit(signum); + } +} + +// Must be called on the main thread. +static void handleSignalMainThread(int signum) { + if (signum >= SIGRTMIN + 1 && signum <= SIGRTMAX) { + for (auto& bar : waybar::Client::inst()->bars) { + bar->handleSignal(signum); + } + + return; + } + + switch (signum) { + case SIGUSR1: + spdlog::debug("Visibility toggled"); + for (auto& bar : waybar::Client::inst()->bars) { + bar->toggle(); + } + break; + case SIGUSR2: + spdlog::info("Reloading..."); + reload = true; + waybar::Client::inst()->reset(); + break; + case SIGINT: + spdlog::info("Quitting."); + reload = false; + waybar::Client::inst()->reset(); + break; + default: + spdlog::debug("Received signal with number {}, but not handling", signum); + break; + } +} + int main(int argc, char* argv[]) { try { auto* client = waybar::Client::inst(); - std::signal(SIGUSR1, [](int /*signal*/) { - for (auto& bar : waybar::Client::inst()->bars) { - bar->toggle(); - } - }); - - std::signal(SIGUSR2, [](int /*signal*/) { - spdlog::info("Reloading..."); - reload = true; - waybar::Client::inst()->reset(); - }); - - std::signal(SIGINT, [](int /*signal*/) { - spdlog::info("Quitting."); - reload = false; - waybar::Client::inst()->reset(); - }); - - for (int sig = SIGRTMIN + 1; sig <= SIGRTMAX; ++sig) { - std::signal(sig, [](int sig) { - for (auto& bar : waybar::Client::inst()->bars) { - bar->handleSignal(sig); - } - }); - } startSignalThread(); + waybar::SafeSignal posix_signal_received; + posix_signal_received.connect([&](int signum) { + handleSignalMainThread(signum); + }); + + std::thread signal_thread([&]() { + catchSignals(posix_signal_received); + }); + + // Every `std::thread` must be joined or detached. + // This thread should run forever, so detach it. + signal_thread.detach(); + auto ret = 0; do { reload = false; From 97591c825a394fc3bedde47b26bed9d605459cdc Mon Sep 17 00:00:00 2001 From: literallyvoid Date: Sat, 12 Apr 2025 16:41:18 -0700 Subject: [PATCH 2/4] Remove `signalThread` and move reaping to `catchSignals` --- src/main.cpp | 78 +++++++++++----------------------------------------- 1 file changed, 16 insertions(+), 62 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index 94355e1b..ba6e00dc 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -14,64 +14,6 @@ std::mutex reap_mtx; std::list reap; volatile bool reload; -void* signalThread(void* args) { - int err; - int signum; - sigset_t mask; - sigemptyset(&mask); - sigaddset(&mask, SIGCHLD); - - while (true) { - err = sigwait(&mask, &signum); - if (err != 0) { - spdlog::error("sigwait failed: {}", strerror(errno)); - continue; - } - - switch (signum) { - case SIGCHLD: - spdlog::debug("Received SIGCHLD in signalThread"); - if (!reap.empty()) { - reap_mtx.lock(); - for (auto it = reap.begin(); it != reap.end(); ++it) { - if (waitpid(*it, nullptr, WNOHANG) == *it) { - spdlog::debug("Reaped child with PID: {}", *it); - it = reap.erase(it); - } - } - reap_mtx.unlock(); - } - break; - default: - spdlog::debug("Received signal with number {}, but not handling", signum); - break; - } - } -} - -void startSignalThread() { - int err; - sigset_t mask; - sigemptyset(&mask); - sigaddset(&mask, SIGCHLD); - - // Block SIGCHLD so it can be handled by the signal thread - // Any threads created by this one (the main thread) should not - // modify their signal mask to unblock SIGCHLD - err = pthread_sigmask(SIG_BLOCK, &mask, nullptr); - if (err != 0) { - spdlog::error("pthread_sigmask failed in startSignalThread: {}", strerror(err)); - exit(1); - } - - pthread_t thread_id; - err = pthread_create(&thread_id, nullptr, signalThread, nullptr); - if (err != 0) { - spdlog::error("pthread_create failed in startSignalThread: {}", strerror(err)); - exit(1); - } -} - static int signal_pipe_write_fd; // Write a single signal to `signal_pipe_write_fd`. @@ -87,8 +29,8 @@ static void writeSignalToPipe(int signum) { // This initializes `signal_pipe_write_fd`, and sets up signal handlers. // // This function will run forever, emitting every `SIGUSR1`, `SIGUSR2`, -// `SIGINT`, and `SIGRTMIN + 1`...`SIGRTMAX` signal received to -// `signal_handler`. +// `SIGINT`, `SIGCHLD`, and `SIGRTMIN + 1`...`SIGRTMAX` signal received +// to `signal_handler`. static void catchSignals(waybar::SafeSignal &signal_handler) { int fd[2]; pipe(fd); @@ -108,6 +50,7 @@ static void catchSignals(waybar::SafeSignal &signal_handler) { std::signal(SIGUSR1, writeSignalToPipe); std::signal(SIGUSR2, writeSignalToPipe); std::signal(SIGINT, writeSignalToPipe); + std::signal(SIGCHLD, writeSignalToPipe); for (int sig = SIGRTMIN + 1; sig <= SIGRTMAX; ++sig) { std::signal(sig, writeSignalToPipe); @@ -156,6 +99,19 @@ static void handleSignalMainThread(int signum) { reload = false; waybar::Client::inst()->reset(); break; + case SIGCHLD: + spdlog::debug("Received SIGCHLD in signalThread"); + if (!reap.empty()) { + reap_mtx.lock(); + for (auto it = reap.begin(); it != reap.end(); ++it) { + if (waitpid(*it, nullptr, WNOHANG) == *it) { + spdlog::debug("Reaped child with PID: {}", *it); + it = reap.erase(it); + } + } + reap_mtx.unlock(); + } + break; default: spdlog::debug("Received signal with number {}, but not handling", signum); break; @@ -166,8 +122,6 @@ int main(int argc, char* argv[]) { try { auto* client = waybar::Client::inst(); - startSignalThread(); - waybar::SafeSignal posix_signal_received; posix_signal_received.connect([&](int signum) { handleSignalMainThread(signum); From dbd3ffd73217506ce519179f460820a870b334b6 Mon Sep 17 00:00:00 2001 From: literallyvoid Date: Sat, 12 Apr 2025 17:48:16 -0700 Subject: [PATCH 3/4] Convert `reload` to a local --- src/main.cpp | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index ba6e00dc..ce493ca1 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -12,7 +12,6 @@ std::mutex reap_mtx; std::list reap; -volatile bool reload; static int signal_pipe_write_fd; @@ -73,7 +72,10 @@ static void catchSignals(waybar::SafeSignal &signal_handler) { } // Must be called on the main thread. -static void handleSignalMainThread(int signum) { +// +// If this signal should restart or close the bar, this function will write +// `true` or `false`, respectively, into `reload`. +static void handleSignalMainThread(int signum, bool &reload) { if (signum >= SIGRTMIN + 1 && signum <= SIGRTMAX) { for (auto& bar : waybar::Client::inst()->bars) { bar->handleSignal(signum); @@ -122,9 +124,11 @@ int main(int argc, char* argv[]) { try { auto* client = waybar::Client::inst(); + bool reload; + waybar::SafeSignal posix_signal_received; posix_signal_received.connect([&](int signum) { - handleSignalMainThread(signum); + handleSignalMainThread(signum, reload); }); std::thread signal_thread([&]() { From 517eb7651e3ea6c7d731e7d9e21d216350d39150 Mon Sep 17 00:00:00 2001 From: literallyvoid Date: Mon, 14 Apr 2025 12:30:08 -0700 Subject: [PATCH 4/4] Run `clang-format` on main.cpp --- src/main.cpp | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index ce493ca1..6e7650a9 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -22,7 +22,7 @@ static void writeSignalToPipe(int signum) { // There's not much we can safely do inside of a signal handler. // Let's just ignore any errors. - (void) amt; + (void)amt; } // This initializes `signal_pipe_write_fd`, and sets up signal handlers. @@ -30,7 +30,7 @@ static void writeSignalToPipe(int signum) { // This function will run forever, emitting every `SIGUSR1`, `SIGUSR2`, // `SIGINT`, `SIGCHLD`, and `SIGRTMIN + 1`...`SIGRTMAX` signal received // to `signal_handler`. -static void catchSignals(waybar::SafeSignal &signal_handler) { +static void catchSignals(waybar::SafeSignal& signal_handler) { int fd[2]; pipe(fd); @@ -72,10 +72,10 @@ static void catchSignals(waybar::SafeSignal &signal_handler) { } // Must be called on the main thread. -// +// // If this signal should restart or close the bar, this function will write // `true` or `false`, respectively, into `reload`. -static void handleSignalMainThread(int signum, bool &reload) { +static void handleSignalMainThread(int signum, bool& reload) { if (signum >= SIGRTMIN + 1 && signum <= SIGRTMAX) { for (auto& bar : waybar::Client::inst()->bars) { bar->handleSignal(signum); @@ -114,7 +114,7 @@ static void handleSignalMainThread(int signum, bool &reload) { reap_mtx.unlock(); } break; - default: + default: spdlog::debug("Received signal with number {}, but not handling", signum); break; } @@ -127,13 +127,9 @@ int main(int argc, char* argv[]) { bool reload; waybar::SafeSignal posix_signal_received; - posix_signal_received.connect([&](int signum) { - handleSignalMainThread(signum, reload); - }); + posix_signal_received.connect([&](int signum) { handleSignalMainThread(signum, reload); }); - std::thread signal_thread([&]() { - catchSignals(posix_signal_received); - }); + std::thread signal_thread([&]() { catchSignals(posix_signal_received); }); // Every `std::thread` must be joined or detached. // This thread should run forever, so detach it.