From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 87C70A00C3; Tue, 21 Jun 2022 23:28:25 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 1EF5F4069C; Tue, 21 Jun 2022 23:28:25 +0200 (CEST) Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by mails.dpdk.org (Postfix) with ESMTP id D761D40151 for ; Tue, 21 Jun 2022 23:28:23 +0200 (CEST) Received: by linux.microsoft.com (Postfix, from userid 1086) id 2296A20C6345; Tue, 21 Jun 2022 14:28:23 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2296A20C6345 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1655846903; bh=LdzGOxQUHrmz//tgUtOE3ue0YIkZxvmkxoFXji9frzk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FFT0JOJk8z33l0aEsXw8PIVVWufPWGYot3mCyEEzsFjfcr63Bh0iuIPACX6q5K+4b Eo3PJlFIJHoLbbmwCnW+svkM7r5XY77POLmDB8hmCf9aRlNUH6Vs3C1Fl/Aww4sI43 hV7Uw8Xu8/k4fEMKqlMY9LlaC7Xlj6ae2MV1u++o= Date: Tue, 21 Jun 2022 14:28:23 -0700 From: Tyler Retzlaff To: Dmitry Kozlyuk Cc: dev@dpdk.org, thomas@monjalon.net, anatoly.burakov@intel.com, Narcisa Vasile Subject: Re: [PATCH v2 2/6] eal: add thread lifetime management Message-ID: <20220621212823.GF18214@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> References: <1654783134-13303-1-git-send-email-roretzla@linux.microsoft.com> <1655250438-18044-1-git-send-email-roretzla@linux.microsoft.com> <1655250438-18044-3-git-send-email-roretzla@linux.microsoft.com> <20220618155908.70e822af@sovereign> <20220621185103.GC18214@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> <20220621224421.244a772f@sovereign> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220621224421.244a772f@sovereign> User-Agent: Mutt/1.5.21 (2010-09-15) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Tue, Jun 21, 2022 at 10:44:21PM +0300, Dmitry Kozlyuk wrote: > 2022-06-21 11:51 (UTC-0700), Tyler Retzlaff: > > > > +int > > > > +rte_thread_join(rte_thread_t thread_id, unsigned long *value_ptr) > > > > +{ > > > > + int ret = 0; > > > > + void *res = NULL; > > > > + void **pres = NULL; > > > > + > > > > + if (value_ptr != NULL) > > > > + pres = &res; > > > > + > > > > + ret = pthread_join((pthread_t)thread_id.opaque_id, pres); > > > > + if (ret != 0) { > > > > + RTE_LOG(DEBUG, EAL, "pthread_join failed\n"); > > > > + return ret; > > > > + } > > > > + > > > > + if (value_ptr != NULL && *pres != NULL) > > > > + *value_ptr = *(unsigned long *)(*pres); > > > > + > > > > + return 0; > > > > +} > > > > > > What makes *pres == NULL special? > > > > it's not clear what you mean, can you explain? maybe there is some > > context i am missing from the original patch series? > > There's no previous context. > After ptread_join(), *pres holds the return value of the thread routine. > You only assign *value_ptr if value_ptr is not NULL (obviously correct) > and if *pres != NULL, that is, if the thread returned a non-NULL value. > But this value is opaque, why do you filter NULL? i don't think it is opaque here? unsigned long * value_ptr says we have to store an integer. which leads to a discussion of what should get stored at the value_ptr location if pthread_join() itself returns no result but the caller of rte_thread_join() requests the result. > Perhaps you meant if (pres != NULL), no dereference? that i think is just a repeat of a test checking if the caller of rte_thread_join is interested in the result? i.e. value_ptr != NULL -> pres != NULL both pres and *pres are dereferenced so it seems to track that prior to those dereferences they have to be validated as being non-NULL. i don't see how we could avoid dereferencing **pres to satisfy the calling contract when the result is requested. now if value_ptr was unsigned long ** i guess i'd understand. i could always be reading the code wrong. but thinking about further there is another problem with this in that we really don't know what is being aliased in *pres when using the pthread implementation, since pthread could be returning a pointer to something narrow or with unknown layout where later dereferencing it as something wider or in this case specifically as unsigned long * would have horrible consequences. i think this ends up semi-related to your other comment about what the result type from rte_thread_func is, we can discuss offline and post details back to the list. > > > > > +int > > > > +rte_thread_create(rte_thread_t *thread_id, > > > > + const rte_thread_attr_t *thread_attr, > > > > + rte_thread_func thread_func, void *args) > > > > +{ > > > > + int ret = 0; > > > > + DWORD tid; > > > > + HANDLE thread_handle = NULL; > > > > + GROUP_AFFINITY thread_affinity; > > > > + struct thread_routine_ctx *ctx = NULL; > > > > + > > > > + ctx = calloc(1, sizeof(*ctx)); > > > > + if (ctx == NULL) { > > > > + RTE_LOG(DEBUG, EAL, "Insufficient memory for thread context allocations\n"); > > > > + ret = ENOMEM; > > > > + goto cleanup; > > > > + } > > > > + ctx->routine_args = args; > > > > + ctx->thread_func = thread_func; > > > > + > > > > + thread_handle = CreateThread(NULL, 0, thread_func_wrapper, ctx, > > > > + CREATE_SUSPENDED, &tid); > > > > + if (thread_handle == NULL) { > > > > + ret = thread_log_last_error("CreateThread()"); > > > > + free(ctx); > > > > + goto cleanup; > > > > > > Missing `free(ctx)` from other error paths below. > > > > beyond this point free(ctx) will happen in thread_func_wrapper. i will > > add a comment to make it clear. > > Not if you exit before ResumeThread() > and thread_func_wrapper() will never execute to call free(). yes, you are right i forgot that this thread is created suspended.