[Fuzzer] Use user signal to coordinate handler shutdown #82067
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This updates the signal handle thread coordinating to use a user signal bit on the SignalHandlerEvent to coordinate shutdown instead of closing the event handle. Closing the event handle is racy as the handle may be closed before the signal handler thread resolves the handle value in _zx_object_wait_many() and we would like to make this an explicit error. Using the user signal bit 1 instead and then closing the event object after the signal handler thread is joined cannot race as the wait will terminate whether the signal is raised before or after the wait begins.
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: James Robinson (jamesr) ChangesThis updates the signal handle thread coordinating to use a user signal bit on the SignalHandlerEvent to coordinate shutdown instead of closing the event handle. Closing the event handle is racy as the handle may be closed before the signal handler thread resolves the handle value in _zx_object_wait_many() and we would like to make this an explicit error. Using the user signal bit 1 instead and then closing the event object after the signal handler thread is joined cannot race as the wait will terminate whether the signal is raised before or after the wait begins. Full diff: https://github.com/llvm/llvm-project/pull/82067.diff 1 Files Affected:
diff --git a/compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp b/compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp
index cfb81cd3f780bb..fe79e1908d6029 100644
--- a/compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp
@@ -292,7 +292,7 @@ void CrashHandler() {
zx_wait_item_t WaitItems[] = {
{
.handle = SignalHandlerEvent,
- .waitfor = ZX_SIGNAL_HANDLE_CLOSED,
+ .waitfor = ZX_USER_SIGNAL_1,
.pending = 0,
},
{
@@ -378,10 +378,11 @@ void CrashHandler() {
}
void StopSignalHandler() {
- _zx_handle_close(SignalHandlerEvent);
+ _zx_object_signal(SignalHandlerEvent, 0, ZX_USER_SIGNAL_1);
if (SignalHandler.joinable()) {
SignalHandler.join();
}
+ _zx_handle_close(SignalHandlerEvent);
}
} // namespace
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@jamesr Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested Please check whether problems have been caused by your change specifically, as How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
This updates the signal handle thread coordinating to use a user signal bit on the SignalHandlerEvent to coordinate shutdown instead of closing the event handle. Closing the event handle is racy as the handle may be closed before the signal handler thread resolves the handle value in _zx_object_wait_many() and we would like to make this an explicit error. Using the user signal bit 1 instead and then closing the event object after the signal handler thread is joined cannot race as the wait will terminate whether the signal is raised before or after the wait begins.