Hi,

On Fri, 2021-08-06 at 19:43 -0700, Namhyung Kim wrote:

On Fri, Jul 30, 2021 at 8:34 AM Riccardo Mancini [off-list ref] wrote:

quoted

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/ (local)

Suggested-by: Alexey Bayduraev <redacted>
Signed-off-by: Riccardo Mancini <redacted>
---

[SNIP]

quoted

@@ -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.

Agree. 
I also need to more clearly separate those APIs too.

quoted

+{
+       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.

ack

quoted

+{
+       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]

quoted

@@ -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.

agreed

quoted

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

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

It's negative, so it needs to be inverted in this case.

Thanks,
Riccardo

Thanks,
Namhyung

quoted

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