[lld] r287794 - Make log(), error() and fatal() thread-safe.

[Sean Silva via llvm-commits]

Even with locking, the output will not be deterministic. Is that something
we are okay with? I think we should avoid it.


-- Sean Silva

On Wed, Nov 23, 2016 at 10:34 AM, Rui Ueyama via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: ruiu
> Date: Wed Nov 23 12:34:28 2016
> New Revision: 287794
>
> URL: http://llvm.org/viewvc/llvm-project?rev=287794&view=rev
> Log:
> Make log(), error() and fatal() thread-safe.
>
> Modified:
>     lld/trunk/ELF/Error.cpp
>
> Modified: lld/trunk/ELF/Error.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Error.
> cpp?rev=287794&r1=287793&r2=287794&view=diff
> ============================================================
> ==================
> --- lld/trunk/ELF/Error.cpp (original)
> +++ lld/trunk/ELF/Error.cpp Wed Nov 23 12:34:28 2016
> @@ -14,6 +14,7 @@
>  #include "llvm/Support/Error.h"
>  #include "llvm/Support/ManagedStatic.h"
>  #include "llvm/Support/raw_ostream.h"
> +#include <mutex>
>
>  #if !defined(_MSC_VER) && !defined(__MINGW32__)
>  #include <unistd.h>
> @@ -28,19 +29,28 @@ uint64_t elf::ErrorCount;
>  raw_ostream *elf::ErrorOS;
>  StringRef elf::Argv0;
>
> +// The functions defined in this file can be called from multiple threads,
> +// but outs() or errs() are not thread-safe. We protect them using a
> mutex.
> +static std::mutex Mu;
> +
>  void elf::log(const Twine &Msg) {
> +  std::lock_guard<std::mutex> Lock(Mu);
>    if (Config->Verbose)
>      outs() << Argv0 << ": " << Msg << "\n";
>  }
>
>  void elf::warn(const Twine &Msg) {
> -  if (Config->FatalWarnings)
> +  if (Config->FatalWarnings) {
>      error(Msg);
> -  else
> -    *ErrorOS << Argv0 << ": warning: " << Msg << "\n";
> +    return;
> +  }
> +  std::lock_guard<std::mutex> Lock(Mu);
> +  *ErrorOS << Argv0 << ": warning: " << Msg << "\n";
>  }
>
>  void elf::error(const Twine &Msg) {
> +  std::lock_guard<std::mutex> Lock(Mu);
> +
>    if (Config->ErrorLimit == 0 || ErrorCount < Config->ErrorLimit) {
>      *ErrorOS << Argv0 << ": error: " << Msg << "\n";
>    } else if (ErrorCount == Config->ErrorLimit) {
> @@ -69,6 +79,7 @@ void elf::exitLld(int Val) {
>  }
>
>  void elf::fatal(const Twine &Msg) {
> +  std::lock_guard<std::mutex> Lock(Mu);
>    *ErrorOS << Argv0 << ": error: " << Msg << "\n";
>    exitLld(1);
>  }
>
>
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