removing legacy code using a selfpipe trick to imitate sigtimedwait o…

…n ancient linux kernels
eteran · Mar 22, 2024 · 0ae5d85 · 0ae5d85
1 parent 2bd3675
commit 0ae5d85
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Showing 2 changed files with 3 additions and 130 deletions.
diff --git a/plugins/DebuggerCore/unix/Posix.cpp b/plugins/DebuggerCore/unix/Posix.cpp
@@ -9,73 +9,21 @@
 
 #include <QProcess>
 
-#ifdef Q_OS_LINUX
-#include <linux/version.h>
-// being very conservative for now, technically this could be
-// as low as 2.6.22
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 0, 0)
-#define USE_SIGTIMEDWAIT
-#endif
-#endif
-
 namespace DebuggerCorePlugin {
 
 namespace {
 
-#if !defined(USE_SIGTIMEDWAIT)
-int selfpipe[2];
-struct sigaction old_action;
-
-/**
- * @brief sigchld_handler
- * @param sig
- * @param info
- * @param p
- */
-void sigchld_handler(int sig, siginfo_t *info, void *p) {
-
-	if (sig == SIGCHLD) {
-		Posix::write(selfpipe[1], " ", sizeof(char));
-	}
-
-	// load as volatile
-	volatile struct sigaction *vsa = &old_action;
-
-	if (old_action.sa_flags & SA_SIGINFO) {
-		using old_action_type       = void (*)(int, siginfo_t *, void *);
-		old_action_type prev_action = vsa->sa_sigaction;
-
-		if (prev_action) {
-			prev_action(sig, info, p);
-		}
-	} else {
-		using old_action_type       = void (*)(int);
-		old_action_type prev_action = vsa->sa_handler;
-
-		if (prev_action && prev_action != SIG_IGN) {
-			prev_action(sig);
-		}
-	}
-}
-
-struct timeval duration_to_timeval(std::chrono::milliseconds msecs) {
-	struct timeval tv;
-	tv.tv_sec  = (msecs.count() / 1000);
-	tv.tv_usec = (msecs.count() % 1000) * 1000;
-	return tv;
-}
-#else
 timespec duration_to_timespec(std::chrono::milliseconds msecs) {
 	struct timespec ts;
 	ts.tv_sec  = (msecs.count() / 1000);
 	ts.tv_nsec = (msecs.count() % 1000) * 1000000;
 	return ts;
 }
-#endif
+
 }
 
 namespace detail {
-namespace {
+
 /**
  * @brief sigtimedwait
  * @param set
@@ -91,7 +39,6 @@ int sigtimedwait(const sigset_t *set, siginfo_t *info, const struct timespec *ti
 	return ret;
 }
 
-}
 }
 
 /**
@@ -156,93 +103,20 @@ pid_t Posix::waitpid(pid_t pid, int *status, int options) {
 	return ret;
 }
 
-#if !defined(USE_SIGTIMEDWAIT)
-/**
- * similar to select but has the timeout specified as a quantity of msecs
- *
- * @brief Posix::select_ex
- * @param nfds
- * @param readfds
- * @param writefds
- * @param exceptfds
- * @param msecs - 0 means wait forever.
- * @return
- */
-int Posix::select_ex(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, std::chrono::milliseconds msecs) {
-	if (msecs.count() != 0) {
-		struct timeval tv = duration_to_timeval(msecs);
-		return Posix::select(nfds, readfds, writefds, exceptfds, &tv);
-	} else {
-		return Posix::select(nfds, readfds, writefds, exceptfds, nullptr);
-	}
-}
-#endif
-
 /**
  * @brief Posix::wait_for_sigchld
  * @param msecs
  * @return
  */
 bool Posix::wait_for_sigchld(std::chrono::milliseconds msecs) {
-#if !defined(USE_SIGTIMEDWAIT)
-	fd_set rfds;
-	FD_ZERO(&rfds);
-	FD_SET(selfpipe[0], &rfds);
-
-	if (Posix::select_ex(selfpipe[0] + 1, &rfds, nullptr, nullptr, msecs) == 0) {
-		return true;
-	}
-
-	char ch;
-	if (Posix::read(selfpipe[0], &ch, sizeof(char)) == -1) {
-		return true;
-	}
-
-	return false;
-#else
+
 	sigset_t mask;
 	siginfo_t info;
 	struct timespec ts = duration_to_timespec(msecs);
 	sigemptyset(&mask);
 	sigaddset(&mask, SIGCHLD);
 
 	return detail::sigtimedwait(&mask, &info, &ts) == SIGCHLD;
-#endif
-}
-
-/**
- * @brief Posix::initialize
- */
-void Posix::initialize() {
-#if !defined(USE_SIGTIMEDWAIT)
-
-	// HACK(eteran): so, the first time we create a QProcess, it will hook SIGCHLD
-	//               unfortunately, in Qt5 it doesn't seem to call our handler
-	//               so we do this to force it to hook BEFORE we do, letting us
-	//               get the first crack at the signal, then we call the one that
-	//               Qt installed.
-	auto p = new QProcess(nullptr);
-	p->start("/bin/true");
-
-	// create a pipe and make it non-blocking
-	int r = ::pipe(selfpipe);
-	Q_UNUSED(r)
-
-	::fcntl(selfpipe[0], F_SETFL, ::fcntl(selfpipe[0], F_GETFL) | O_NONBLOCK);
-	::fcntl(selfpipe[1], F_SETFL, ::fcntl(selfpipe[1], F_GETFL) | O_NONBLOCK);
-
-	// setup a signal handler
-	struct sigaction new_action = {};
-
-	new_action.sa_sigaction = sigchld_handler;
-	new_action.sa_flags     = SA_RESTART | SA_SIGINFO;
-	sigemptyset(&new_action.sa_mask);
-
-	sigaction(SIGCHLD, &new_action, &old_action);
-#else
-	// TODO(eteran): the man pages mention blocking the signal we want to catch
-	//               but I'm not sure if it is necessary for this use case...
-#endif
 }
 
 }
diff --git a/plugins/DebuggerCore/unix/linux/DebuggerCore.cpp b/plugins/DebuggerCore/unix/linux/DebuggerCore.cpp
@@ -184,7 +184,6 @@ DebuggerCore::DebuggerCore()
 	  userStackSegment_(osIs64Bit_ ? 0x2b : 0x7b)
 #endif
 {
-	Posix::initialize();
 
 	feature::detect_proc_access(&procMemReadBroken_, &procMemWriteBroken_);