BillyONeal created this revision.
BillyONeal added reviewers: EricWF, mclow.lists.
Herald added a subscriber: jfb.
- Repair thread-unsafe modifications of n_alive in F.pass.cpp
In this example, the ctor of G runs in the main thread in the expression G(),
and also in the copy ctor of G() in the DECAY_COPY inside std::thread. The main
thread destroys the G() instance at the semicolon, and the started thread
destroys the G() after it returns. Thus there is a race between the threads on
the n_alive variable.
The fix is to join with the background thread before attempting to destroy the
G in the main thread.
- Repair a race in detach.pass.cpp by adding atomic.
This test thinks that setting done = true as the last line in the thread
procedure is equivalent to joining with it, but that is not true. There is a
race between destroying the G instance in main and destroying the *parameter*
of the thread procedure. This problem is avoided by making n_alive and op_run
atomics.
https://reviews.llvm.org/D50549
Files:
test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
Index:
test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
===================================================================
---
test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
+++
test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
@@ -29,8 +29,8 @@
int alive_;
bool done_;
public:
- static int n_alive;
- static bool op_run;
+ static std::atomic_int n_alive;
+ static std::atomic_bool op_run;
G() : alive_(1), done_(false)
{
@@ -57,8 +57,8 @@
}
};
-int G::n_alive = 0;
-bool G::op_run = false;
+std::atomic_int G::n_alive = 0;
+std::atomic_bool G::op_run = false;
void foo() {}
Index:
test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
===================================================================
---
test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
+++
test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
@@ -157,8 +157,11 @@
{
assert(G::n_alive == 0);
assert(!G::op_run);
- std::thread t((G()));
- t.join();
+ {
+ G g;
+ std::thread t(g);
+ t.join();
+ }
assert(G::n_alive == 0);
assert(G::op_run);
}
@@ -185,8 +188,11 @@
{
assert(G::n_alive == 0);
assert(!G::op_run);
- std::thread t(G(), 5, 5.5);
- t.join();
+ {
+ G g;
+ std::thread t(g, 5, 5.5);
+ t.join();
+ }
assert(G::n_alive == 0);
assert(G::op_run);
}
Index: test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
===================================================================
--- test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
+++ test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp
@@ -29,8 +29,8 @@
int alive_;
bool done_;
public:
- static int n_alive;
- static bool op_run;
+ static std::atomic_int n_alive;
+ static std::atomic_bool op_run;
G() : alive_(1), done_(false)
{
@@ -57,8 +57,8 @@
}
};
-int G::n_alive = 0;
-bool G::op_run = false;
+std::atomic_int G::n_alive = 0;
+std::atomic_bool G::op_run = false;
void foo() {}
Index: test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
===================================================================
--- test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
+++ test/std/thread/thread.threads/thread.thread.class/thread.thread.constr/F.pass.cpp
@@ -157,8 +157,11 @@
{
assert(G::n_alive == 0);
assert(!G::op_run);
- std::thread t((G()));
- t.join();
+ {
+ G g;
+ std::thread t(g);
+ t.join();
+ }
assert(G::n_alive == 0);
assert(G::op_run);
}
@@ -185,8 +188,11 @@
{
assert(G::n_alive == 0);
assert(!G::op_run);
- std::thread t(G(), 5, 5.5);
- t.join();
+ {
+ G g;
+ std::thread t(g, 5, 5.5);
+ t.join();
+ }
assert(G::n_alive == 0);
assert(G::op_run);
}
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
