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From: Ammar Nofan Faizi <[email protected]>
To: Alviro Iskandar Setiawan <[email protected]>
Cc: Ammar Faizi <[email protected]>,
	Muhammad Rizki <[email protected]>,
	Kanna Scarlet <[email protected]>,
	GNU/Weeb Mailing List <[email protected]>
Subject: Re: [RFC PATCH v1 2/2] chnet: Implement `get_thread()` and `put_thread()` function
Date: Mon, 29 Aug 2022 12:48:31 +0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAOG64qOCpyGwGv2TwV5yTnsPk7Hvv-O_mh+1bnu2VPAoPAZsVg@mail.gmail.com>

On 8/29/22 12:38 PM, Alviro Iskandar Setiawan wrote:
> On Mon, Aug 29, 2022 at 12:29 PM Ammar Nofan Faizi wrote:
>> On 8/29/22 12:24 PM, Alviro Iskandar Setiawan wrote:
>>> On Mon, Aug 29, 2022 at 12:17 PM Alviro Iskandar Setiawan wrote:
>>>> On Mon, Aug 29, 2022 at 11:54 AM Ammar Nofan Faizi wrote:
>>>>> On 8/29/22 11:41 AM, Alviro Iskandar Setiawan wrote:
>>>>>> On Mon, Aug 29, 2022 at 8:11 AM Ammar Faizi wrote:
>>>>>>> +static base::Thread *get_thread(void)
>>>>>>> +{
>>>>>>> +       const uint32_t max_ch_thpool = g_max_ch_thpool;
>>>>>>> +       const uint32_t nr_ref_split = 2048;
>>>>>>> +       struct ch_thpool **thp;
>>>>>>> +       struct ch_thpool *ret = nullptr;
>>>>>>> +       struct ch_thpool *tmp;
>>>>>>> +       uint32_t min_ref_idx;
>>>>>>> +       uint32_t min_ref;
>>>>>>> +       uint32_t i;
>>>>>>> +
>>>>>>> +       g_thpool_lock_.lock();
>>>>>>> +       thp = g_thpool;
>>>>>>> +       if (!thp) {
>>>>>>> +               g_thpool_lock_.unlock();
>>>>>>> +               return nullptr;
>>>>>>> +       }
>>>>>>
>>>>>> in what situation @thp can be nullptr?
>>>>>
>>>>> When the chnet_global_destroy() is called.
>>>
>>> btw, i missed a case on the chnet construction, you do
>>>
>>>      thread_(*get_thread()),
>>>
>>> if get_thread() returns a nullptr, the @thread_ will become a
>>> reference to a nullptr, it will definitely break, how do you handle
>>> this?
>>
>> I don't think we need to handle that. If @thp ever be a nullptr in a
>> get_thread() call, then it's a misuse of the API. We must never call
>> get_thread() after chnet_global_destroy() is called. It doesn't make
>> much sense to have this situation.
> 
> if this should never happen, then why do you do a null check there?
> your null check doesn't make much sense too! why are we returning
> nullptr if we exactly know that the caller will randomly fault if that
> happens, i can't accept your reasoning

OK.

Fine, let's omit that nullptr return. To assert that path, we perform a
CHECK() assertion, so it will just crash the whole program with a full
call traces if the contract is violated. This way also makes debugging
process easier. Are you happy with this change?

Incremental is:

diff --git a/chnet/chnet.cc b/chnet/chnet.cc
index 782e4fe..fc536d2 100644
--- a/chnet/chnet.cc
+++ b/chnet/chnet.cc
@@ -647,10 +647,7 @@ static base::Thread *get_thread(void)
  
  	g_thpool_lock_.lock();
  	thp = g_thpool;
-	if (!thp) {
-		g_thpool_lock_.unlock();
-		return nullptr;
-	}
+	CHECK(thp);
  
  	tmp = thp[0];
  	if (!tmp) {

-- 
Ammar Faizi

  reply	other threads:[~2022-08-29  5:50 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-29  1:11 [RFC PATCH v1 0/2] Fixed number of chromium workers Ammar Faizi
2022-08-29  1:11 ` [RFC PATCH v1 1/2] chnet: Prepare global struct ch_thpool array Ammar Faizi
2022-08-29  4:21   ` Alviro Iskandar Setiawan
2022-08-29  4:47     ` Ammar Nofan Faizi
2022-08-29  1:11 ` [RFC PATCH v1 2/2] chnet: Implement `get_thread()` and `put_thread()` function Ammar Faizi
2022-08-29  4:41   ` Alviro Iskandar Setiawan
2022-08-29  4:54     ` Ammar Nofan Faizi
2022-08-29  5:17       ` Alviro Iskandar Setiawan
2022-08-29  5:24         ` Alviro Iskandar Setiawan
2022-08-29  5:29           ` Ammar Nofan Faizi
2022-08-29  5:38             ` Alviro Iskandar Setiawan
2022-08-29  5:48               ` Ammar Nofan Faizi [this message]
2022-08-29  6:01                 ` Alviro Iskandar Setiawan

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