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Fix concurrent tool installation race conditions with named mutex #51834

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Fix concurrent tool installation race conditions with named mutex #51834

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078c682
Initial plan
Copilot Nov 20, 2025
75fc903
Add mutex protection for concurrent tool installations
Copilot Nov 20, 2025
e779d23
Improve mutex UX with initial quick check and waiting message
Copilot Nov 20, 2025
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6 changes: 6 additions & 0 deletions src/Cli/dotnet/CliStrings.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -431,6 +431,12 @@ setx PATH "%PATH%;{0}"
<data name="FailedToFindStagedToolPackage" xml:space="preserve">
<value>Failed to find staged tool package '{0}'.</value>
</data>
<data name="ToolInstallationTimeout" xml:space="preserve">
<value>Timeout waiting for concurrent installation of tool '{0}' version '{1}' to complete. Please try again.</value>
</data>
<data name="ToolInstallationWaiting" xml:space="preserve">
<value>Another installation of tool '{0}' version '{1}' is in progress. Waiting for it to complete... (Press Ctrl+C to cancel)</value>
</data>
<data name="ColumnMaxWidthMustBeGreaterThanZero" xml:space="preserve">
<value>Column maximum width must be greater than zero.</value>
</data>
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54 changes: 44 additions & 10 deletions src/Cli/dotnet/ToolPackage/ToolPackageDownloaderBase.cs
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Expand Up @@ -272,26 +272,60 @@ protected void DownloadTool(
string? targetFramework,
VerbosityOptions verbosity)
{
// Use a named mutex to serialize concurrent installations of the same tool package
string mutexName = GetToolInstallMutexName(packageId, packageVersion);
using var mutex = new Mutex(false, mutexName);

if (!IsPackageInstalled(packageId, packageVersion, packageDownloadDir.Value))
try
{
DownloadAndExtractPackage(packageId, nugetPackageDownloader, packageDownloadDir.Value, packageVersion, packageSourceLocation, includeUnlisted: givenSpecificVersion, verbosity: verbosity);
}
// First try a quick check to see if the mutex is immediately available
if (!mutex.WaitOne(TimeSpan.FromMilliseconds(50)))
{
// Mutex is held by another process - inform the user
Reporter.Error.WriteLine(string.Format(CliStrings.ToolInstallationWaiting, packageId, packageVersion));
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The waiting message is written to Reporter.Error, but this is informational rather than an error. According to the PR description, this message is meant to provide "transparency about what's happening." Consider using Reporter.Output instead, as this is normal operational information, not an error condition.

Reporter.Output.WriteLine(string.Format(CliStrings.ToolInstallationWaiting, packageId, packageVersion));
Suggested change
Reporter.Error.WriteLine(string.Format(CliStrings.ToolInstallationWaiting, packageId, packageVersion));
Reporter.Output.WriteLine(string.Format(CliStrings.ToolInstallationWaiting, packageId, packageVersion));

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CreateAssetFile(packageId, packageVersion, packageDownloadDir, Path.Combine(assetFileDirectory.Value, ToolPackageInstance.AssetsFileName), _runtimeJsonPath, verbosity, targetFramework);
// Now wait for the longer duration
if (!mutex.WaitOne(TimeSpan.FromMinutes(5)))
{
throw new ToolPackageException(string.Format(CliStrings.ToolInstallationTimeout, packageId, packageVersion));
}
}
Comment on lines +279 to +292
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The mutex acquisition logic should handle AbandonedMutexException, which can be thrown when a previous process holding the mutex terminated abnormally without releasing it. When this exception is caught, the calling thread has acquired the mutex and can safely proceed with the installation. Consider wrapping the WaitOne calls in a try-catch block that handles AbandonedMutexException.

Example:

try
{
    if (!mutex.WaitOne(TimeSpan.FromMilliseconds(50)))
    {
        // ... existing code ...
    }
}
catch (AbandonedMutexException)
{
    // Mutex was abandoned by another process, but we now own it
    // This is safe to proceed
}

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// Also download RID-specific package if needed
if (ResolveRidSpecificPackage(packageId, packageVersion, packageDownloadDir, assetFileDirectory, verbosity) is PackageId ridSpecificPackage)
{
if (!IsPackageInstalled(ridSpecificPackage, packageVersion, packageDownloadDir.Value))
if (!IsPackageInstalled(packageId, packageVersion, packageDownloadDir.Value))
{
DownloadAndExtractPackage(ridSpecificPackage, nugetPackageDownloader, packageDownloadDir.Value, packageVersion, packageSourceLocation, includeUnlisted: true, verbosity: verbosity);
DownloadAndExtractPackage(packageId, nugetPackageDownloader, packageDownloadDir.Value, packageVersion, packageSourceLocation, includeUnlisted: givenSpecificVersion, verbosity: verbosity);
}

CreateAssetFile(ridSpecificPackage, packageVersion, packageDownloadDir, Path.Combine(assetFileDirectory.Value, ToolPackageInstance.RidSpecificPackageAssetsFileName), _runtimeJsonPath, verbosity, targetFramework);
CreateAssetFile(packageId, packageVersion, packageDownloadDir, Path.Combine(assetFileDirectory.Value, ToolPackageInstance.AssetsFileName), _runtimeJsonPath, verbosity, targetFramework);

// Also download RID-specific package if needed
if (ResolveRidSpecificPackage(packageId, packageVersion, packageDownloadDir, assetFileDirectory, verbosity) is PackageId ridSpecificPackage)
{
if (!IsPackageInstalled(ridSpecificPackage, packageVersion, packageDownloadDir.Value))
{
DownloadAndExtractPackage(ridSpecificPackage, nugetPackageDownloader, packageDownloadDir.Value, packageVersion, packageSourceLocation, includeUnlisted: true, verbosity: verbosity);
}

CreateAssetFile(ridSpecificPackage, packageVersion, packageDownloadDir, Path.Combine(assetFileDirectory.Value, ToolPackageInstance.RidSpecificPackageAssetsFileName), _runtimeJsonPath, verbosity, targetFramework);
}
}
finally
{
mutex.ReleaseMutex();
}
Comment on lines +312 to 315
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The ReleaseMutex() call in the finally block can throw ApplicationException if the mutex is not currently owned by the calling thread (e.g., if an exception was thrown before the mutex was acquired, or if an AbandonedMutexException occurred but wasn't properly caught). This could mask the original exception. Consider checking if the mutex was successfully acquired before attempting to release it.

Example:

bool mutexAcquired = false;
try
{
    if (!mutex.WaitOne(TimeSpan.FromMilliseconds(50)))
    {
        // ...
        mutexAcquired = mutex.WaitOne(TimeSpan.FromMinutes(5));
    }
    else
    {
        mutexAcquired = true;
    }
    
    if (mutexAcquired)
    {
        // ... installation logic ...
    }
}
finally
{
    if (mutexAcquired)
    {
        mutex.ReleaseMutex();
    }
}

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}

private static string GetToolInstallMutexName(PackageId packageId, NuGetVersion packageVersion)
{
// Create a mutex name in the format: tool-install-{packageId}-{packageVersion}
// Replace characters that are invalid in mutex names with underscores
string safeName = $"tool-install-{packageId}-{packageVersion.ToNormalizedString()}"
.Replace('/', '_')
.Replace('\\', '_');

return safeName;
}
Comment on lines +318 to +327
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The mutex name sanitization only replaces / and \ characters, but mutex names on Windows have additional restrictions. Windows mutex names:

  1. Cannot exceed 260 characters
  2. Cannot contain certain special characters beyond / and \

Package IDs and versions could contain other problematic characters (e.g., + in semver build metadata). Consider using a more robust sanitization approach or creating a hash-based name for long/complex package identifiers.

Example:

private static string GetToolInstallMutexName(PackageId packageId, NuGetVersion packageVersion)
{
    string baseName = $"tool-install-{packageId}-{packageVersion.ToNormalizedString()}";
    
    // If the name is too long or contains problematic characters, use a hash
    if (baseName.Length > 200 || !IsValidMutexName(baseName))
    {
        using var sha256 = SHA256.Create();
        var hash = Convert.ToBase64String(sha256.ComputeHash(Encoding.UTF8.GetBytes(baseName)))
            .Replace('/', '_')
            .Replace('+', '-');
        return $"tool-install-{hash}";
    }
    
    return baseName.Replace('/', '_').Replace('\\', '_');
}

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public bool TryGetDownloadedTool(
PackageId packageId,
NuGetVersion packageVersion,
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10 changes: 10 additions & 0 deletions src/Cli/dotnet/xlf/CliStrings.cs.xlf
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