Fix the SIGINT handlers

amccarth-google · amccarth-google · commit 6c84ffbf5fd9 · 2017-09-20T18:09:39.000Z
1. Fix a data race (g_interrupt_sent flag usage was not thread safe, signals can be handled on arbitrary threads) 2. exit() is not signal-safe, replaced it with the signal-safe equivalent _exit() (This differs from the patch on Phabrictor because I had to add `#include <atomic>` to get the definition of `std::atomic_flag`.) patch by lemo Differential Revision: https://reviews.llvm.org/D37926 llvm-svn: 313785
diff --git a/lldb/tools/driver/Driver.cpp b/lldb/tools/driver/Driver.cpp
@@ -9,6 +9,7 @@
 
 #include "Driver.h"
 
+#include <atomic>
 #include <csignal>
 #include <fcntl.h>
 #include <limits.h>
@@ -1177,17 +1178,16 @@ void sigwinch_handler(int signo) {
 }
 
 void sigint_handler(int signo) {
-  static bool g_interrupt_sent = false;
+  static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
   if (g_driver) {
-    if (!g_interrupt_sent) {
-      g_interrupt_sent = true;
+    if (!g_interrupt_sent.test_and_set()) {
       g_driver->GetDebugger().DispatchInputInterrupt();
-      g_interrupt_sent = false;
+      g_interrupt_sent.clear();
       return;
     }
   }
 
-  exit(signo);
+  _exit(signo);
 }
 
 void sigtstp_handler(int signo) {
diff --git a/lldb/tools/lldb-mi/MIDriverMain.cpp b/lldb/tools/lldb-mi/MIDriverMain.cpp
@@ -33,6 +33,7 @@
 
 // Third party headers:
 #include "lldb/API/SBHostOS.h"
+#include <atomic>
 #include <csignal>
 #include <stdio.h>
 
@@ -72,14 +73,13 @@ void sigint_handler(int vSigno) {
 #ifdef _WIN32 // Restore handler as it is not persistent on Windows
   signal(SIGINT, sigint_handler);
 #endif
-  static bool g_interrupt_sent = false;
+  static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
   CMIDriverMgr &rDriverMgr = CMIDriverMgr::Instance();
   lldb::SBDebugger *pDebugger = rDriverMgr.DriverGetTheDebugger();
   if (pDebugger != nullptr) {
-    if (!g_interrupt_sent) {
-      g_interrupt_sent = true;
+    if (!g_interrupt_sent.test_and_set()) {
       pDebugger->DispatchInputInterrupt();
-      g_interrupt_sent = false;
+      g_interrupt_sent.clear();
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,7 @@`
`9`	`9`
`10`	`10`	`#include "Driver.h"`
`11`	`11`
	`12`	`+#include <atomic>`
`12`	`13`	`#include <csignal>`
`13`	`14`	`#include <fcntl.h>`
`14`	`15`	`#include <limits.h>`
`@@ -1177,17 +1178,16 @@ void sigwinch_handler(int signo) {`
`1177`	`1178`	`}`
`1178`	`1179`
`1179`	`1180`	`void sigint_handler(int signo) {`
`1180`		`- static bool g_interrupt_sent = false;`
	`1181`	`+ static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;`
`1181`	`1182`	`if (g_driver) {`
`1182`		`- if (!g_interrupt_sent) {`
`1183`		`- g_interrupt_sent = true;`
	`1183`	`+ if (!g_interrupt_sent.test_and_set()) {`
`1184`	`1184`	`g_driver->GetDebugger().DispatchInputInterrupt();`
`1185`		`- g_interrupt_sent = false;`
	`1185`	`+ g_interrupt_sent.clear();`
`1186`	`1186`	`return;`
`1187`	`1187`	`}`
`1188`	`1188`	`}`
`1189`	`1189`
`1190`		`- exit(signo);`
	`1190`	`+ _exit(signo);`
`1191`	`1191`	`}`
`1192`	`1192`
`1193`	`1193`	`void sigtstp_handler(int signo) {`