Re: [dpdk-dev] [PATCH v2 1/6] eal: add function that sets thread name

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

2021-06-18 18:57 (UTC-0700), Narcisa Ana Maria Vasile:
> From: Narcisa Vasile <navasile@microsoft.com>
> 
> Implement function that sets the name of a thread.
> On Windows, SetThreadDescription() is used. Use GetProcAddress()
> to obtain the address of the function for MinGW compatibility.
> 
> Depends-on: series-17402 ("eal: Add EAL API for threading")
> 
> Signed-off-by: Narcisa Vasile <navasile@microsoft.com>
> ---
>  lib/eal/common/rte_thread.c  | 17 ++++++++++
>  lib/eal/include/rte_thread.h | 18 +++++++++++
>  lib/eal/version.map          |  1 +
>  lib/eal/windows/rte_thread.c | 60 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 96 insertions(+)
[...]
> diff --git a/lib/eal/include/rte_thread.h b/lib/eal/include/rte_thread.h
> index 40da83467b..c65cfd8c9e 100644
> --- a/lib/eal/include/rte_thread.h
> +++ b/lib/eal/include/rte_thread.h
> @@ -24,6 +24,8 @@ extern "C" {
>  
>  #include <sched.h>
>  
> +#define RTE_THREAD_MAX_DESCRIPTION_LENGTH   16
> +

Why export this constant?

>  /**
>   * Thread id descriptor.
>   */
> @@ -439,6 +441,22 @@ int rte_thread_barrier_wait(rte_thread_barrier *barrier);
>  __rte_experimental
>  int rte_thread_barrier_destroy(rte_thread_barrier *barrier);
>  
> +/**
> + * Set the name of the thread represented by 'thread_id'.
> + *
> + * @param thread_id
> + *   The id of the thread.
> + *
> + * @param name
> + *   Thread name to set.
> + *
> + * @return
> + *   On success, return 0.
> + *    On failure, return a positive errno-style error number.

Typo: extra space.

> + */
> +__rte_experimental
> +int rte_thread_name_set(rte_thread_t thread_id, const char *name);
> +

There is `rte_thread_setname(pthread_t id, const char * name, size_t len)`.
I assume it should be deprecated in favor of this new API
via a notice in `deprecation.rst`.

>  /**
>   * Create a TLS data key visible to all threads in the process.
>   * the created key is later used to get/set a value.
> diff --git a/lib/eal/version.map b/lib/eal/version.map
> index 6645f60a78..2a566c04af 100644
> --- a/lib/eal/version.map
> +++ b/lib/eal/version.map
> @@ -443,6 +443,7 @@ EXPERIMENTAL {
>  	rte_thread_barrier_init;
>  	rte_thread_barrier_wait;
>  	rte_thread_barrier_destroy;
> +	rte_thread_name_set;
>  };
>  
>  INTERNAL {
> diff --git a/lib/eal/windows/rte_thread.c b/lib/eal/windows/rte_thread.c
> index b2ff16f51f..995ae2491d 100644
> --- a/lib/eal/windows/rte_thread.c
> +++ b/lib/eal/windows/rte_thread.c
> @@ -556,6 +556,66 @@ rte_thread_barrier_destroy(rte_thread_barrier *barrier)
>  	return 0;
>  }
>  
> +typedef HRESULT
> +(*SetThreadDescription_type)(HANDLE thread_handle, PCWSTR thread_description);
> +
> +int
> +rte_thread_name_set(rte_thread_t thread_id, const char *name)
> +{
> +	int ret = 0;
> +	size_t count;
> +	HRESULT hr;
> +	HANDLE thread_handle = NULL;
> +	WCHAR w_name[RTE_THREAD_MAX_DESCRIPTION_LENGTH];
> +	HMODULE kernel_lib = NULL;
> +	SetThreadDescription_type SetThreadDescription_ptr;
> +
> +	static const char library_name[] = "kernel32.dll";
> +	static const char function[] = "SetThreadDescription";
> +
> +	kernel_lib = LoadLibraryA(library_name);
> +	if (kernel_lib == NULL) {
> +		ret = thread_log_last_error("LoadLibraryA(\"kernel32.dll\")");
> +		goto cleanup;
> +	}

Rather then locate the function every time (kernel32.dll is always loaded),
what do you think of using `RTE_INIT`/`RTE_FINI` for that?

> +
> +	SetThreadDescription_ptr = (SetThreadDescription_type)(
> +			(void *)GetProcAddress(kernel_lib, function));
> +	if (SetThreadDescription_ptr == NULL) {
> +		ret = thread_log_last_error("GetProcAddress(\"kernel32.dll\", \"SetThreadDescription\")");
> +		goto cleanup;
> +	}
> +
> +	thread_handle = OpenThread(THREAD_SET_LIMITED_INFORMATION, FALSE,
> +			thread_id.opaque_id);
> +	if (thread_handle == NULL) {
> +		ret = thread_log_last_error("OpenThread()");
> +		goto cleanup;
> +	}
> +
> +	count = mbstowcs(w_name, name, RTE_THREAD_MAX_DESCRIPTION_LENGTH);

It's better to use `RTE_DIM(w_name)`, this way named constant is not needed.

> +	if (count < 0) {
> +		RTE_LOG(DEBUG, EAL, "Invalid thread name!\n");
> +		ret = EINVAL;
> +		goto cleanup;
> +	}
> +
> +	hr = SetThreadDescription_ptr(thread_handle, w_name);
> +	if (FAILED(hr)) {
> +		ret = thread_log_last_error("SetThreadDescription()");
> +		goto cleanup;
> +	}
> +
> +cleanup:
> +	if (kernel_lib != NULL)
> +		FreeLibrary(kernel_lib);
> +	if (thread_handle != NULL) {
> +		CloseHandle(thread_handle);
> +		thread_handle = NULL;

Such local variable assignments on cleanup are useless.

> +	}
> +	return ret;
> +}
> +
>  int
>  rte_thread_key_create(rte_thread_key *key,
>  		__rte_unused void (*destructor)(void *))