r228604 - Diagnose timeouts in the LockFileManager and delete the dead lock file

[Richard Smith]

On Mon, Feb 9, 2015 at 12:35 PM, Ben Langmuir <blangmuir at apple.com> wrote:

> Author: benlangmuir
> Date: Mon Feb  9 14:35:13 2015
> New Revision: 228604
>
> URL: http://llvm.org/viewvc/llvm-project?rev=228604&view=rev
> Log:
> Diagnose timeouts in the LockFileManager and delete the dead lock file
>
> If the lock file manager times out, we should give an error rather than
> silently trying to load the existing module.  And delete the
> (presumably) dead lock file, since it will otherwise prevent progress in
> future invokations. This is unsound since we have no way to prove that
> the lock file we are deleting is the same one we timed out on, but since
> the lock is only to avoid excessive rebuilding anyway it should be okay.
> Depends on llvm r228603.
>

This diagnostic fires a *lot* when, say, bootstrapping Clang with modules
enabled at -j16. Is the timeout perhaps too short?


> Modified:
>     cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td
>     cfe/trunk/lib/Frontend/CompilerInstance.cpp
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td?rev=228604&r1=228603&r2=228604&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td Mon Feb  9
> 14:35:13 2015
> @@ -83,6 +83,8 @@ def err_module_not_found : Error<"module
>  def err_module_not_built : Error<"could not build module '%0'">,
> DefaultFatal;
>  def err_module_lock_failure : Error<
>    "could not acquire lock file for module '%0'">, DefaultFatal;
> +def err_module_lock_timeout : Error<
> +  "timed out waiting to acquire lock file for module '%0'">, DefaultFatal;
>  def err_module_cycle : Error<"cyclic dependency in module '%0': %1">,
>    DefaultFatal;
>  def note_pragma_entered_here : Note<"#pragma entered here">;
>
> Modified: cfe/trunk/lib/Frontend/CompilerInstance.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/CompilerInstance.cpp?rev=228604&r1=228603&r2=228604&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Frontend/CompilerInstance.cpp (original)
> +++ cfe/trunk/lib/Frontend/CompilerInstance.cpp Mon Feb  9 14:35:13 2015
> @@ -1022,9 +1022,19 @@ static bool compileAndLoadModule(Compile
>      case llvm::LockFileManager::LFS_Shared:
>        // Someone else is responsible for building the module. Wait for
> them to
>        // finish.
> -      if (Locked.waitForUnlock() == llvm::LockFileManager::Res_OwnerDied)
> +      switch (Locked.waitForUnlock()) {
> +      case llvm::LockFileManager::Res_Success:
> +        ModuleLoadCapabilities |= ASTReader::ARR_OutOfDate;
> +        break;
> +      case llvm::LockFileManager::Res_OwnerDied:
>          continue; // try again to get the lock.
> -      ModuleLoadCapabilities |= ASTReader::ARR_OutOfDate;
> +      case llvm::LockFileManager::Res_Timeout:
> +        Diags.Report(ModuleNameLoc, diag::err_module_lock_timeout)
> +            << Module->Name;
> +        // Clear the lock file so that future invokations can make
> progress.
> +        Locked.unsafeRemoveLockFile();
> +        return false;
> +      }
>        break;
>      }
>
>
>
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