From 88f5bf77f92899b19fdafdffc7b060f930c1cb8b Mon Sep 17 00:00:00 2001 From: Calixte Denizet Date: Tue, 3 Dec 2019 10:32:25 +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 Reviewed By: marco-c, dmajor Subscribers: froydnj, dmajor, dberris, jfb, #sanitizers, llvm-commits, sylvestre.ledru Tags: #sanitizers, #llvm Differential Revision: https://reviews.llvm.org/D70910 --- compiler-rt/lib/profile/GCDAProfiling.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/compiler-rt/lib/profile/GCDAProfiling.c b/compiler-rt/lib/profile/GCDAProfiling.c index 498c059..93d226f 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_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 +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 __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 -- 2.7.4