[PATCH] Thread: Fix setThreadAffinity issue

[Barnabás Pőcze]

Hi


2024. december 2., hétfő 10:04 keltezéssel, Harvey Yang <chenghaoyang at chromium.org> írta:

> This fixes commit 4d9db06d669044c0c461a2aed79c85c7fe32a502.
> 
> Previously we call Thread::setThreadAffinityInternal in
> Thread::startThread, which seems to lead to a SEGV in
> pthread_setaffinity_np.

I believe the patch should describe what the cause is. As far as I can
see it's a data race on `Thread::thread_` where it is concurrently set
and read from `Thread::start()` and `Thread::startThread()`, respectively.


> 
> This patch moves the call after the construction of std::thread.
> 

Should probably have:

  Fixes: 4d9db06d66 ("libcamera: add method to set thread affinity")


> Signed-off-by: Harvey Yang <chenghaoyang at chromium.org>
> ---
>  src/libcamera/base/thread.cpp | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
> index f6322fe31..319bfda9a 100644
> --- a/src/libcamera/base/thread.cpp
> +++ b/src/libcamera/base/thread.cpp
> @@ -257,6 +257,8 @@ void Thread::start()
>  	data_->exit_.store(false, std::memory_order_relaxed);
> 
>  	thread_ = std::thread(&Thread::startThread, this);
> +
> +	setThreadAffinityInternal();
>  }
> 
>  void Thread::startThread()
> @@ -284,8 +286,6 @@ void Thread::startThread()
>  	data_->tid_ = syscall(SYS_gettid);
>  	currentThreadData = data_;
> 
> -	setThreadAffinityInternal();
> -
>  	run();
>  }
> 
> --
> 2.47.0.338.g60cca15819-goog
> 


Regards,
Barnabás Pőcze