[PATCH] D115574: [ThinLTO] Fix nondeterministic exit on error.
Mircea Trofin via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 10 21:00:55 PST 2021
mtrofin created this revision.
mtrofin added a reviewer: tejohnson.
Herald added subscribers: ormris, steven_wu, mgrang, hiraditya, inglorion.
mtrofin requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
In the multi-threaded case, if a thread hits an error, we mimick
LLVMContext's behavior of reporting the error and exit-ing. However,
this doesn't cleanly join the other threads, so depending on how fast
the process exits, other threads may report 'terminate called without an
active exception'.
To avoid this non-determinsim, and without introducing a more complicated
design, we just report the error, but not exit early, in the
multi-threaded case. We do track whether we hit errors and exit(1) after
joining.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D115574
Files:
llvm/tools/llvm-lto2/llvm-lto2.cpp
Index: llvm/tools/llvm-lto2/llvm-lto2.cpp
===================================================================
--- llvm/tools/llvm-lto2/llvm-lto2.cpp
+++ llvm/tools/llvm-lto2/llvm-lto2.cpp
@@ -29,6 +29,7 @@
#include "llvm/Support/PluginLoader.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/Threading.h"
+#include <atomic>
using namespace llvm;
using namespace lto;
@@ -236,13 +237,6 @@
std::vector<std::unique_ptr<MemoryBuffer>> MBs;
Config Conf;
- Conf.DiagHandler = [](const DiagnosticInfo &DI) {
- DiagnosticPrinterRawOStream DP(errs());
- DI.print(DP);
- errs() << '\n';
- if (DI.getSeverity() == DS_Error)
- exit(1);
- };
Conf.CPU = codegen::getMCPU();
Conf.Options = codegen::InitTargetOptionsFromCodeGenFlags(Triple());
@@ -314,9 +308,30 @@
else
Backend = createInProcessThinBackend(
llvm::heavyweight_hardware_concurrency(Threads));
+ const bool SingleThreaded = ThinLTODistributedIndexes;
+ // Track whether we hit an error; in particular, in the multi-threaded case,
+ // we can't exit() early because the rest of the threads wouldn't have had a
+ // change to be join-ed, and that would result in a "terminate called without
+ // an active exception". Altogether, this results in nondeterministic
+ // behavior. Instead, we don't exit in the multi-threaded case, but we make
+ // sure to report the error and then at the end (after joining cleanly)
+ // exit(1).
+ std::atomic<bool> HasErrors;
+ std::atomic_init(&HasErrors, false);
+ Conf.DiagHandler = [&](const DiagnosticInfo &DI) {
+ DiagnosticPrinterRawOStream DP(errs());
+ DI.print(DP);
+ errs() << '\n';
+ if (DI.getSeverity() != DS_Error)
+ return;
+ if (SingleThreaded)
+ exit(1);
+ else
+ HasErrors = true;
+ };
+
LTO Lto(std::move(Conf), std::move(Backend));
- bool HasErrors = false;
for (std::string F : InputFilenames) {
std::unique_ptr<MemoryBuffer> MB = check(MemoryBuffer::getFile(F), F);
std::unique_ptr<InputFile> Input =
@@ -381,7 +396,7 @@
"failed to create cache");
check(Lto.run(AddStream, Cache), "LTO::run failed");
- return 0;
+ return static_cast<int>(HasErrors);
}
static int dumpSymtab(int argc, char **argv) {
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