Em Thu, Jul 15, 2021 at 06:31:07PM +0200, Riccardo Mancini escreveu:

Hi Arnaldo,

thanks for reviewing the patch!

On Wed, 2021-07-14 at 11:16 -0300, Arnaldo Carvalho de Melo wrote:
<SNIP>

quoted

quoted

+
+enum threadpool_status {
+       THREADPOOL_STATUS__STOPPED,             /* no threads */
+       THREADPOOL_STATUS__ERROR,               /* errors */
+       THREADPOOL_STATUS__MAX
+};
+
+struct threadpool_struct {

Can this be just 'struct threadpool'? I think its descriptive enough:

I agree, but I wanted to keep the naming consistent between workqueue.c and
threadpool.c.

quoted

quoted

+       int                     nr_threads;     /* number of threads in the
pool */
+       struct thread_struct    *threads;       /* array of threads in the
pool */
+       struct task_struct      *current_task;  /* current executing
function
*/
+       enum threadpool_status  status;         /* current status of the
pool
*/
+};
+
+struct thread_struct {
+       int                             idx;    /* idx of thread in pool-

quoted

threads */

+       pid_t                           tid;    /* tid of thread */
+       struct threadpool_struct        *pool;  /* parent threadpool */
+       struct {
+               int from[2];                    /* messages from thread
(acks)
*/
+               int to[2];                      /* messages to thread
(commands) */
+       } pipes;
+};

This one, since we have already a 'struct thread' in tools/perf, to
represent a PERF_RECORD_FORK, perhaps we can call it 'struct
threadpool_entry'?

Agreed.

quoted

quoted

+
+/**
+ * init_pipes - initialize all pipes of @thread
+ */
+static void init_pipes(struct thread_struct *thread)
+{
+       thread->pipes.from[0] = -1;
+       thread->pipes.from[1] = -1;
+       thread->pipes.to[0] = -1;
+       thread->pipes.to[1] = -1;
+}
+
+/**
+ * open_pipes - open all pipes of @thread
+ */
+static int open_pipes(struct thread_struct *thread)

Here please:

threadpool_entry__open_pipes()

Its longer, but helps with ctags/cscope navigation and we can go
directly to it via:

:ta threadpool_entry__open_p<TAB>

While 'ta: open_pipes' may bo to various places where this idiom is
used.

Agreed.

<SNIP>

quoted

quoted

+/**
+ * create_threadpool - create a fixed threadpool with @n_threads threads
+ */
+struct threadpool_struct *create_threadpool(int n_threads)

Is this already something the kernel has and thus we should keep the
naming? I couldn't find it in the kernel, so please name it:

struct threadpool *threadpool__new(int nthreads)

As before, I did this to keep consistency with workqueue.
Since this threadpool+workqueue can be a standalone library, I preferred to keep
the naming consistent inside it, instead of making it consistent with perf (this
is what I was referring to in the cover letter, not just the workqueue API).
What do you think?
I also prefer perf's naming conventions, but it'd feel strange to use two
different naming conventions inside the same library.

See my comment on the other message about this naming dilemma :-)
 

quoted

quoted

+{
+       int ret, t;
+       struct threadpool_struct *pool = malloc(sizeof(*pool));
+
+       if (!pool) {
+               pr_err("threadpool: cannot allocate pool: %s\n",
+                       strerror(errno));o

Humm, pr_err() at this level isn't appropriate, please make callers
complain.

ok.

quoted

quoted

+               return NULL;
+       }
+
+       if (n_threads <= 0) {
+               pr_err("threadpool: invalid number of threads: %d\n",
+                       n_threads);

pr_debug()

ok

quoted

quoted

+               goto out_free_pool;
+       }
+
+       pool->nr_threads = n_threads;
+       pool->current_task = NULL;
+
+       pool->threads = malloc(n_threads * sizeof(*pool->threads));
+       if (!pool->threads) {
+               pr_err("threadpool: cannot allocate threads: %s\n",
+                       strerror(errno));
+               goto out_free_pool;
+       }
+
+       for (t = 0; t < n_threads; t++) {
+               pool->threads[t].idx = t;
+               pool->threads[t].tid = -1;
+               pool->threads[t].pool = pool;
+               init_pipes(&pool->threads[t]);
+       }
+
+       for (t = 0; t < n_threads; t++) {
+               ret = open_pipes(&pool->threads[t]);
+               if (ret)
+                       goto out_close_pipes;
+       }
+
+       pool->status = THREADPOOL_STATUS__STOPPED;
+
+       return pool;
+
+out_close_pipes:
+       for (t = 0; t < n_threads; t++)
+               close_pipes(&pool->threads[t]);
+
+       free(pool->threads);
+out_free_pool:
+       free(pool);
+       return NULL;

Here we can use ERR_PTR()/PTR_ERR() to let the caller know what was the
problem, i.e. we can ditch all the pr_err/pr_debug(), etc and instead
have a threadpool__strerror(struct threadpool *pool, int err) like we
have for 'struct evsel', please take a look at evsel__open_strerror().

Thanks, I'll have a look at it.
So, what I sould do is not use pr_* higher than debug inside library code and
return meaningful errors through PR_ERR, right?

Right.
 

quoted

quoted

+}
+
+/**
+ * destroy_threadpool - free the @pool and all its resources
+ */
+void destroy_threadpool(struct threadpool_struct *pool)

void threadpool__delete(struct threadpool *pool)

quoted

+{
+       int t;
+
+       if (!pool)
+               return;
+
+       WARN_ON(pool->status != THREADPOOL_STATUS__STOPPED
+               && pool->status != THREADPOOL_STATUS__ERROR);
+
+       for (t = 0; t < pool->nr_threads; t++)
+               close_pipes(&pool->threads[t]);

reset pool->threads[t] to -1

already inside close_pipes. I agree it might be confusing without the
threadpool_entry__ prefix.

quoted

quoted

+
+       free(pool->threads);

zfree

In general, when should I use zfree instead of free?

quoted

quoted

+       free(pool);
+}
+
+/**
+ * threadpool_size - get number of threads in the threadpool
+ */
+int threadpool_size(struct threadpool_struct *pool)

  
threadpool__size()

ok

Thanks,
Riccardo

quoted

quoted

+{
+       return pool->nr_threads;
+}

diff --git a/tools/perf/util/workqueue/threadpool.h

b/tools/perf/util/workqueue/threadpool.h
new file mode 100644
index 0000000000000000..2b9388c768a0b588

--- /dev/null
+++ b/tools/perf/util/workqueue/threadpool.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __WORKQUEUE_THREADPOOL_H
+#define __WORKQUEUE_THREADPOOL_H
+
+struct threadpool_struct;
+struct task_struct;
+
+typedef void (*task_func_t)(int tidx, struct task_struct *task);
+
+struct task_struct {
+       task_func_t fn;
+};
+
+extern struct threadpool_struct *create_threadpool(int n_threads);
+extern void destroy_threadpool(struct threadpool_struct *pool);
+
+extern int threadpool_size(struct threadpool_struct *pool);
+
+#endif /* __WORKQUEUE_THREADPOOL_H */

-- 
2.31.1

-- 

- Arnaldo