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63c381f336
Summary: Before this patch, signal handling wasn't signal safe. This leads to real-world crashes. It used ManagedStatic inside of signals, this can allocate and can lead to unexpected state when a signal occurs during llvm_shutdown (because llvm_shutdown destroys the ManagedStatic). It also used cl::opt without custom backing storage. Some de-allocation was performed as well. Acquiring a lock in a signal handler is also a great way to deadlock. We can't just disable signals on llvm_shutdown because the signals might do useful work during that shutdown. We also can't just disable llvm_shutdown for programs (instead of library uses of clang) because we'd have to then mark the pointers as not leaked and make sure all the ManagedStatic uses are OK to leak and remain so. Move all of the code to lock-free datastructures instead, and avoid having any of them in an inconsistent state. I'm not trying to be fancy, I'm not using any explicit memory order because this code isn't hot. The only purpose of the atomics is to guarantee that a signal firing on the same or a different thread doesn't see an inconsistent state and crash. In some cases we might miss some state (for example, we might fail to delete a temporary file), but that's fine. Note that I haven't touched any of the backtrace support despite it not technically being totally signal-safe. When that code is called we know something bad is up and we don't expect to continue execution, so calling something that e.g. sets errno is the least of our problems. A similar patch should be applied to lib/Support/Windows/Signals.inc, but that can be done separately. Fix r332428 which I reverted in r332429. I originally used double-wide CAS because I was lazy, but some platforms use a runtime function for that which thankfully failed to link (it would have been bad for signal handlers otherwise). I use a separate flag to guard the data instead. <rdar://problem/28010281> Reviewers: dexonsmith Subscribers: steven_wu, llvm-commits llvm-svn: 332496
80 lines
3.2 KiB
C++
80 lines
3.2 KiB
C++
//===- llvm/Support/Signals.h - Signal Handling support ----------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines some helpful functions for dealing with the possibility of
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// unix signals occurring while your program is running.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_SIGNALS_H
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#define LLVM_SUPPORT_SIGNALS_H
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#include <string>
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namespace llvm {
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class StringRef;
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class raw_ostream;
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namespace sys {
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/// This function runs all the registered interrupt handlers, including the
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/// removal of files registered by RemoveFileOnSignal.
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void RunInterruptHandlers();
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/// This function registers signal handlers to ensure that if a signal gets
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/// delivered that the named file is removed.
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/// Remove a file if a fatal signal occurs.
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bool RemoveFileOnSignal(StringRef Filename, std::string* ErrMsg = nullptr);
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/// This function removes a file from the list of files to be removed on
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/// signal delivery.
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void DontRemoveFileOnSignal(StringRef Filename);
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/// When an error signal (such as SIGABRT or SIGSEGV) is delivered to the
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/// process, print a stack trace and then exit.
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/// Print a stack trace if a fatal signal occurs.
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/// \param Argv0 the current binary name, used to find the symbolizer
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/// relative to the current binary before searching $PATH; can be
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/// StringRef(), in which case we will only search $PATH.
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/// \param DisableCrashReporting if \c true, disable the normal crash
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/// reporting mechanisms on the underlying operating system.
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void PrintStackTraceOnErrorSignal(StringRef Argv0,
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bool DisableCrashReporting = false);
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/// Disable all system dialog boxes that appear when the process crashes.
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void DisableSystemDialogsOnCrash();
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/// Print the stack trace using the given \c raw_ostream object.
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void PrintStackTrace(raw_ostream &OS);
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// Run all registered signal handlers.
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void RunSignalHandlers();
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using SignalHandlerCallback = void (*)(void *);
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/// Add a function to be called when an abort/kill signal is delivered to the
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/// process. The handler can have a cookie passed to it to identify what
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/// instance of the handler it is.
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void AddSignalHandler(SignalHandlerCallback FnPtr, void *Cookie);
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/// This function registers a function to be called when the user "interrupts"
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/// the program (typically by pressing ctrl-c). When the user interrupts the
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/// program, the specified interrupt function is called instead of the program
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/// being killed, and the interrupt function automatically disabled. Note
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/// that interrupt functions are not allowed to call any non-reentrant
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/// functions. An null interrupt function pointer disables the current
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/// installed function. Note also that the handler may be executed on a
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/// different thread on some platforms.
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/// Register a function to be called when ctrl-c is pressed.
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void SetInterruptFunction(void (*IF)());
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} // End sys namespace
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} // End llvm namespace
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#endif
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