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SubjectRe: [RFC PATCH v2 03/10] perf workqueue: add threadpool start and stop functions
On Fri, Jul 30, 2021 at 8:34 AM Riccardo Mancini <rickyman7@gmail.com> wrote:
>
> 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@linux.intel.com/
>
> Suggested-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
> Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
> ---

[SNIP]
> @@ -93,6 +134,130 @@ static void threadpool_entry__close_pipes(struct threadpool_entry *thread)
> }
> }
>
> +/**
> + * threadpool__wait_thread - receive ack from thread
> + *
> + * NB: call only from main thread!
> + */
> +static int threadpool__wait_thread(struct threadpool_entry *thread)

If you wanted to differentiate APIs for main thread, I think it's better
to pass the pool struct (according to the name) and the index like:

int threadpool__wait_thread(struct threadpool *pool, int idx)

Then it can get a pointer to the entry easily.

> +{
> + int res;
> + enum threadpool_msg msg = THREADPOOL_MSG__UNDEFINED;
> +
> + res = readn(thread->pipes.ack[0], &msg, sizeof(msg));
> + if (res < 0) {
> + pr_debug2("threadpool: failed to recv msg from tid=%d: %s\n",
> + thread->tid, strerror(errno));
> + return -THREADPOOL_ERROR__READPIPE;
> + }
> + if (msg != THREADPOOL_MSG__ACK) {
> + pr_debug2("threadpool: received unexpected msg from tid=%d: %s\n",
> + thread->tid, threadpool_msg_tags[msg]);
> + return -THREADPOOL_ERROR__INVALIDMSG;
> + }
> +
> + pr_debug2("threadpool: received ack from tid=%d\n", thread->tid);
> +
> + return 0;
> +}
> +
> +/**
> + * threadpool__terminate_thread - send stop signal to thread and wait for ack
> + *
> + * NB: call only from main thread!
> + */
> +static int threadpool__terminate_thread(struct threadpool_entry *thread)

Ditto.

> +{
> + int res;
> + enum threadpool_msg msg = THREADPOOL_MSG__STOP;
> +
> + res = writen(thread->pipes.cmd[1], &msg, sizeof(msg));
> + if (res < 0) {
> + pr_debug2("threadpool: error sending stop msg to tid=%d: %s\n",
> + thread->tid, strerror(errno));
> + return -THREADPOOL_ERROR__WRITEPIPE;
> + }
> +
> + return threadpool__wait_thread(thread);
> +}
> +

[SNIP]
> @@ -161,12 +326,30 @@ struct threadpool *threadpool__new(int n_threads)
> *
> * Buffer size should be at least THREADPOOL_STRERR_BUFSIZE bytes.
> */
> -int threadpool__strerror(struct threadpool *pool __maybe_unused, int err, char *buf, size_t size)
> +int threadpool__strerror(struct threadpool *pool, int err, char *buf, size_t size)
> {
> char sbuf[STRERR_BUFSIZE], *emsg;
> + const char *status_str, *errno_str;
>
> - emsg = str_error_r(err, sbuf, sizeof(sbuf));
> - return scnprintf(buf, size, "Error: %s.\n", emsg);
> + status_str = IS_ERR_OR_NULL(pool) ? "error" : threadpool_status_tags[pool->status];
> +
> + switch (err) {
> + case -THREADPOOL_ERROR__SIGPROCMASK:
> + case -THREADPOOL_ERROR__READPIPE:
> + case -THREADPOOL_ERROR__WRITEPIPE:
> + emsg = str_error_r(errno, sbuf, sizeof(sbuf));
> + errno_str = threadpool_errno_str[-err-THREADPOOL_ERROR__OFFSET];
> + return scnprintf(buf, size, "%s: %s.\n", errno_str, emsg);
> + case -THREADPOOL_ERROR__INVALIDMSG:
> + errno_str = threadpool_errno_str[-err-THREADPOOL_ERROR__OFFSET];
> + return scnprintf(buf, size, "%s.\n", errno_str);
> + case -THREADPOOL_ERROR__NOTALLOWED:
> + return scnprintf(buf, size, "%s (%s).\n",
> + threadpool_errno_str[-err], status_str);

s/-err/-err-THREADPOOL_ERROR__OFFSET/ ?

It'd be nice if you calculate the index once.

> + default:
> + emsg = str_error_r(err, sbuf, sizeof(sbuf));

I'm confused whether the 'err' is negative or positive?

Thanks,
Namhyung


> + return scnprintf(buf, size, "Error: %s", emsg);
> + }
> }
>

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