Re: [RFC PATCH 03/10] perf workqueue: add threadpool start and stop functions

[Riccardo Mancini]

Hi Arnaldo,

On Wed, 2021-07-14 at 12:15 -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jul 13, 2021 at 02:11:14PM +0200, Riccardo Mancini escreveu:
> > This patch adds the start and stop functions, alongside the thread
> > function.
> > Each thread will run until a stop signal is received.
> > Furthermore, start and stop are added to the test.
> > 
> > Thread management is based on the prototype from Alexey:
> > https://lore.kernel.org/lkml/cover.1625227739.git.alexey.v.bayduraev@xxxxxxxxxxxxxxx/
> > 
> > Suggested-by: Alexey Bayduraev <alexey.v.bayduraev@xxxxxxxxxxxxxxx>
> > Signed-off-by: Riccardo Mancini <rickyman7@xxxxxxxxx>
<SNIP>
> >  
> >  static int __threadpool__teardown(struct threadpool_struct *pool)
> >  {
> > +       int ret;
> > +
> > +       ret = stop_threadpool(pool);
> 
>         int ret = stop_threadpool(pool);

ok

> 
> > +       TEST_ASSERT_VAL("threadpool start failure", ret == 0);
> > +       TEST_ASSERT_VAL("stopped threadpool is ready",
> > +                       !threadpool_is_ready(pool));
> > +
> >         destroy_threadpool(pool);
> >  
> >         return 0;
> > diff --git a/tools/perf/util/workqueue/threadpool.c
> > b/tools/perf/util/workqueue/threadpool.c
> > index 70c67569f956a3e2..f4635ff782b9388e 100644
> > --- a/tools/perf/util/workqueue/threadpool.c
> > +++ b/tools/perf/util/workqueue/threadpool.c
> > @@ -4,12 +4,23 @@
> >  #include <unistd.h>
> >  #include <errno.h>
> >  #include <string.h>
> > +#include <pthread.h>
> > +#include <signal.h>
> > +#include <syscall.h>
> >  #include "debug.h"
> >  #include "asm/bug.h"
> >  #include "threadpool.h"
> >  
> > +#ifndef HAVE_GETTID
> > +static inline pid_t gettid(void)
> > +{
> > +       return (pid_t)syscall(__NR_gettid);
> > +}
> > +#endif
> 
> Isn't this defined elsewhere? Yeah, when we decide to move it to
> tools/lib/workqueue/ we'll need it, but for now, reduce patch size.

No, it's just statically defined in tools/perf/jvmti/jvmti_agent.c.
I saw there is a libc_compat.h header in tools/include/tools, I could put this
definition there, and remove the one from jvmti_agent.c.

<SNIP>
> > +/**
> > + * wait_thread - receive ack from thread
> > + *
> > + * NB: call only from main thread!
> > + */
> > +static int wait_thread(struct thread_struct *thread)
> > +{
> > +       int res;
> > +       enum thread_msg msg = THREAD_MSG__UNDEFINED;
> > +
> > +       res = read(thread->pipes.from[0], &msg, sizeof(msg));
> 
>         int res = read(thread->pipes.from[0], &msg, sizeof(msg));

ok

<SNIP>
> > +/**
> > + * threadpool_thread - function running on thread
> > + *
> > + * This function waits for a signal from main thread to start executing
> > + * a task.
> > + * On completion, it will go back to sleep, waiting for another signal.
> > + * Signals are delivered through pipes.
> > + */
> > +static void *threadpool_thread(void *args)
> 
>    threadpool_function()
> 
>  ETOMANY 'thread' in a name.

Agreed :)

<SNIP>

> > +/**
> > + * start_threadpool - start all threads in the pool.
> > + *
> > + * The function blocks until all threads are up and running.
> > + */
> > +int start_threadpool(struct threadpool_struct *pool)
> 
> int threadpool__start(struct threadpool *pool)

ok

> 
> > +{
> > +       int err;
> > +
> > +       if (pool->status != THREADPOOL_STATUS__STOPPED) {
> > +               pr_err("threadpool: starting not stopped pool\n");
> > +               return -1;
> > +       }
> > +
> > +       err = __start_threadpool(pool);
> > +       pool->status = err ? THREADPOOL_STATUS__ERROR :
> > THREADPOOL_STATUS__READY;
> > +       return err;
> > +}
> > +
> > +/**
> > + * stop_threadpool - stop all threads in the pool.
> > + *
> > + * This function blocks waiting for ack from all threads.
> > + */
> > +int stop_threadpool(struct threadpool_struct *pool)
> 
> int threadpool__stop(struct threadpool *pool)

ok

> 
> > +{
> > +       int t, ret, err = 0;
> > +
> > +       if (pool->status != THREADPOOL_STATUS__READY) {
> > +               pr_err("threadpool: stopping not ready pool\n");
> > +               return -1;
> > +       }
> > +
> > +       for (t = 0; t < pool->nr_threads; t++) {
> > +               ret = terminate_thread(&pool->threads[t]);
> > +               if (ret && !err)
> > +                       err = -1;
> > +       }
> > +
> > +       pool->status = err ? THREADPOOL_STATUS__ERROR :
> > THREADPOOL_STATUS__STOPPED;
> > +
> > +       return err;
> > +}
> > +
> > +/**
> > + * threadpool_is_ready - check if the threads are running
> > + */
> > +bool threadpool_is_ready(struct threadpool_struct *pool)
> 
> bool threadpool__is_ready(struct threadpool *pool)

ok

Thanks,
Riccardo

> 
> > +{
> > +       return pool->status == THREADPOOL_STATUS__READY;
> > +}
> > diff --git a/tools/perf/util/workqueue/threadpool.h
> > b/tools/perf/util/workqueue/threadpool.h
> > index 2b9388c768a0b588..b62cad2b2c5dd331 100644
> > --- a/tools/perf/util/workqueue/threadpool.h
> > +++ b/tools/perf/util/workqueue/threadpool.h
> > @@ -14,6 +14,11 @@ struct task_struct {
> >  extern struct threadpool_struct *create_threadpool(int n_threads);
> >  extern void destroy_threadpool(struct threadpool_struct *pool);
> >  
> > +extern int start_threadpool(struct threadpool_struct *pool);
> > +extern int stop_threadpool(struct threadpool_struct *pool);
> > +
> >  extern int threadpool_size(struct threadpool_struct *pool);
> >  
> > +extern bool threadpool_is_ready(struct threadpool_struct *pool);
> > +
> >  #endif /* __WORKQUEUE_THREADPOOL_H */
> > -- 
> > 2.31.1
> > 
>