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From 02ce9d8ef5a84bc884de4105eae5f8736ef67634 Mon Sep 17 00:00:00 2001
From: Calixte Denizet <calixte.denizet@gmail.com>
Date: Tue, 10 Dec 2019 13:22:33 +0100
Subject: [PATCH] [compiler-rt] Add a critical section when flushing gcov
counters
Summary:
Counters can be flushed in a multi-threaded context for example when the process is forked in different threads (https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp#L632-L663).
In order to avoid pretty bad things, a critical section is needed around the flush.
We had a lot of crashes in this code in Firefox CI when we switched to clang for linux ccov builds and those crashes disappeared with this patch.
Reviewers: marco-c, froydnj, dmajor, davidxl, vsk
Reviewed By: marco-c, dmajor
Subscribers: ahatanak, froydnj, dmajor, dberris, jfb, #sanitizers, llvm-commits, sylvestre.ledru
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70910
---
diff --git a/compiler-rt/lib/profile/GCDAProfiling.c b/compiler-rt/lib/profile/GCDAProfiling.c
index b7257db10e7..d4abc4181ed 100644
--- a/compiler-rt/lib/profile/GCDAProfiling.c
+++ b/compiler-rt/lib/profile/GCDAProfiling.c
@@ -62,8 +62,27 @@ typedef unsigned long long uint64_t;
#include "InstrProfiling.h"
#include "InstrProfilingUtil.h"
-/* #define DEBUG_GCDAPROFILING */
+#ifndef _WIN32
+#include <pthread.h>
+static pthread_mutex_t gcov_flush_mutex = PTHREAD_MUTEX_INITIALIZER;
+static __inline void gcov_flush_lock() {
+ pthread_mutex_lock(&gcov_flush_mutex);
+}
+static __inline void gcov_flush_unlock() {
+ pthread_mutex_unlock(&gcov_flush_mutex);
+}
+#else
+#include <windows.h>
+static SRWLOCK gcov_flush_mutex = SRWLOCK_INIT;
+static __inline void gcov_flush_lock() {
+ AcquireSRWLockExclusive(&gcov_flush_mutex);
+}
+static __inline void gcov_flush_unlock() {
+ ReleaseSRWLockExclusive(&gcov_flush_mutex);
+}
+#endif
+/* #define DEBUG_GCDAPROFILING */
/*
* --- GCOV file format I/O primitives ---
*/
@@ -620,12 +639,16 @@ void llvm_register_flush_function(fn_ptr fn) {
}
void __custom_llvm_gcov_flush() {
+ gcov_flush_lock();
+
struct fn_node* curr = flush_fn_list.head;
while (curr) {
curr->fn();
curr = curr->next;
}
+
+ gcov_flush_unlock();
}
COMPILER_RT_VISIBILITY
--
2.24.0
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