[vlc-devel] [PATCH v3 1/4] thread: add a function to give names to threads

[Steve Lhomme]

v3 contains the missing Android variant (adapted from a similar call in 
KitKat).

On 2020-11-10 12:05, Steve Lhomme wrote:
> Given the amount of threads used by VLC it can be useful to known which thread
> is what when debugging or in a backtrace (especially if the stack is bogus, we
> can get a hint at where the thread comes from).
> 
> This feature is supported in the Windows debugger when used on Windows 10 1607
> and upper. There might be support in gdb on other platforms as well.
> 
> The posix variants comes from dav1d.
> ---
>   include/vlc_threads.h | 10 ++++++++++
>   src/android/thread.c  |  8 ++++++++
>   src/libvlccore.sym    |  1 +
>   src/os2/thread.c      |  5 +++++
>   src/posix/thread.c    | 23 +++++++++++++++++++++++
>   src/win32/thread.c    | 21 +++++++++++++++++++++
>   6 files changed, 68 insertions(+)
> 
> diff --git a/include/vlc_threads.h b/include/vlc_threads.h
> index 21f4e46c278..46490334eb8 100644
> --- a/include/vlc_threads.h
> +++ b/include/vlc_threads.h
> @@ -750,6 +750,16 @@ void vlc_atomic_notify_all(void *addr);
>   VLC_API int vlc_clone(vlc_thread_t *th, void *(*entry)(void *), void *data,
>                         int priority) VLC_USED;
>   
> +/**
> + * Set the thread name of the current thread.
> + *
> + * \param name the string to use as the thread name
> + *
> + * \note On Linux the name can be up to 16 bytes long, including the terminating
> + * null byte on Linux. If larger the name will be truncated.
> + */
> +VLC_API void vlc_thread_set_name(const char *name);
> +
>   /**
>    * Marks a thread as cancelled.
>    *
> diff --git a/src/android/thread.c b/src/android/thread.c
> index 79132be2e46..02dad44d083 100644
> --- a/src/android/thread.c
> +++ b/src/android/thread.c
> @@ -195,6 +195,14 @@ int vlc_set_priority (vlc_thread_t th, int priority)
>       return VLC_SUCCESS;
>   }
>   
> +void vlc_thread_set_name(const char *name)
> +{
> +    char buf[16];       // MAX_TASK_COMM_LEN=16 is hard-coded into bionic
> +    strncpy(buf, name, 15);
> +    buf[15] = '\0';
> +    pthread_setname_np(pthread_self(), buf);
> +}
> +
>   void vlc_cancel (vlc_thread_t thread_id)
>   {
>       atomic_uint *addr;
> diff --git a/src/libvlccore.sym b/src/libvlccore.sym
> index c4d5273dbd5..8b149ae2b74 100644
> --- a/src/libvlccore.sym
> +++ b/src/libvlccore.sym
> @@ -616,6 +616,7 @@ vlc_interrupt_register
>   vlc_interrupt_unregister
>   vlc_killed
>   vlc_join
> +vlc_thread_set_name
>   vlc_list_children
>   vlc_meta_AddExtra
>   vlc_meta_CopyExtraNames
> diff --git a/src/os2/thread.c b/src/os2/thread.c
> index 822b3f3b26c..cce326efc29 100644
> --- a/src/os2/thread.c
> +++ b/src/os2/thread.c
> @@ -355,6 +355,11 @@ unsigned long vlc_thread_id (void)
>       return _gettid();
>   }
>   
> +void vlc_thread_set_name(const char *name)
> +{
> +    VLC_UNUSED(name);
> +}
> +
>   /*** Thread cancellation ***/
>   
>   /* APC procedure for thread cancellation */
> diff --git a/src/posix/thread.c b/src/posix/thread.c
> index 91eab74716d..930ba72e64d 100644
> --- a/src/posix/thread.c
> +++ b/src/posix/thread.c
> @@ -238,6 +238,29 @@ int vlc_set_priority (vlc_thread_t th, int priority)
>       return VLC_SUCCESS;
>   }
>   
> +#ifdef __linux__
> +#include <sys/prctl.h>
> +void vlc_thread_set_name(const char *name)
> +{
> +    prctl(PR_SET_NAME, name);
> +}
> +#elif defined(__APPLE__)
> +void vlc_thread_set_name(const char *name)
> +{
> +    pthread_setname_np(name);
> +}
> +#elif defined(__NetBSD__)
> +void vlc_thread_set_name(const char *name)
> +{
> +    pthread_setname_np(pthread_self(), "%s", (void*)name);
> +}
> +#else
> +void vlc_thread_set_name(const char *name)
> +{
> +    VLC_UNUSED(name);
> +}
> +#endif
> +
>   void vlc_cancel(vlc_thread_t th)
>   {
>       pthread_cancel(th.handle);
> diff --git a/src/win32/thread.c b/src/win32/thread.c
> index 60b4232e047..b2787a08adf 100644
> --- a/src/win32/thread.c
> +++ b/src/win32/thread.c
> @@ -31,6 +31,7 @@
>   
>   #define _DECL_DLLMAIN
>   #include <vlc_common.h>
> +#include <vlc_charset.h>
>   
>   #include "libvlc.h"
>   #include <stdarg.h>
> @@ -165,6 +166,7 @@ retry:
>   }
>   
>   /*** Futeces^WAddress waits ***/
> +static HRESULT (WINAPI *SetThreadDescription_)(HANDLE, PCWSTR);
>   #if (_WIN32_WINNT < _WIN32_WINNT_WIN8)
>   static BOOL (WINAPI *WaitOnAddress_)(VOID volatile *, PVOID, SIZE_T, DWORD);
>   #define WaitOnAddress (*WaitOnAddress_)
> @@ -429,6 +431,16 @@ int vlc_set_priority (vlc_thread_t th, int priority)
>       return VLC_SUCCESS;
>   }
>   
> +void vlc_thread_set_name(const char *name)
> +{
> +    if (SetThreadDescription_)
> +    {
> +        wchar_t *wname = ToWide(name);
> +        SetThreadDescription_(GetCurrentThread(), wname);
> +        free(wname);
> +    }
> +}
> +
>   /*** Thread cancellation ***/
>   
>   #if IS_INTERRUPTIBLE
> @@ -809,6 +821,15 @@ BOOL WINAPI DllMain (HANDLE hinstDll, DWORD fdwReason, LPVOID lpvReserved)
>                   WakeByAddressAll_ = WakeByAddressFallback;
>                   WakeByAddressSingle_ = WakeByAddressFallback;
>               }
> +            LOOKUP(SetThreadDescription);
> +#else
> +            HMODULE h = GetModuleHandle(TEXT("kernel32.dll"));
> +            if (h == NULL)
> +                h = GetModuleHandle(TEXT("api-ms-win-core-processthreads-l1-1-3.dll"));
> +            if (h != NULL)
> +                LOOKUP(SetThreadDescription);
> +            else
> +                SetThreadDescription_ = NULL;
>   #endif
>               thread_key = TlsAlloc();
>               if (unlikely(thread_key == TLS_OUT_OF_INDEXES))
> -- 
> 2.26.2
> 
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