[Lldb-commits] [PATCH] Do not pass an invalid thread to Thread{Cancel, Join}.

[Greg Clayton]

All patches look good. Feel free to submit them anytime.

On Jan 11, 2011, at 7:54 PM, Stephen Wilson wrote:

> 
> A race condition exists between StopReadThread and the reader thread proper.
> When StopReadThread sets m_read_thread_enabled to false the reader thread can
> terminate and set m_read_thread to LLDB_INVALID_HOST_THREAD on exit.  Thus calls
> to ThreadCancel or ThreadJoin in StopReadThread can be passed an invalid handle.
> 
> This patch removes the race by using m_read_thread_enabled as the flag thru
> which the reader thread can notify the parent thread of early/abnormal
> termination.
> 
> 
> diff --git a/source/Core/Communication.cpp b/source/Core/Communication.cpp
> index 99c619d..b178657 100644
> --- a/source/Core/Communication.cpp
> +++ b/source/Core/Communication.cpp
> @@ -138,7 +138,7 @@ Communication::Read (void *dst, size_t dst_len, uint32_t timeout_usec, Connectio
>                                          timeout_usec, 
>                                          m_connection_sp.get());
> 
> -    if (m_read_thread != LLDB_INVALID_HOST_THREAD)
> +    if (m_read_thread_enabled)
>     {
>         // We have a dedicated read thread that is getting data for us
>         size_t cached_bytes = GetCachedBytes (dst, dst_len);
> @@ -257,8 +257,9 @@ Communication::StopReadThread (Error *error_ptr)
> 
>     Host::ThreadCancel (m_read_thread, error_ptr);
> 
> -    return Host::ThreadJoin (m_read_thread, NULL, error_ptr);
> +    bool status = Host::ThreadJoin (m_read_thread, NULL, error_ptr);
>     m_read_thread = LLDB_INVALID_HOST_THREAD;
> +    return status;
> }
> 
> 
> @@ -317,7 +318,7 @@ Communication::ReadFromConnection (void *dst, size_t dst_len, ConnectionStatus &
> bool
> Communication::ReadThreadIsRunning ()
> {
> -    return m_read_thread != LLDB_INVALID_HOST_THREAD;
> +    return m_read_thread_enabled;
> }
> 
> void *
> @@ -370,7 +371,7 @@ Communication::ReadThread (void *p)
> 
>     // Let clients know that this thread is exiting
>     comm->BroadcastEvent (eBroadcastBitReadThreadDidExit);
> -    comm->m_read_thread = LLDB_INVALID_HOST_THREAD;
> +    comm->m_read_thread_enabled = false;
>     comm->Disconnect();
>     return NULL;
> }
> -- 
> 1.7.3.5
> 
> 
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