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 BEEB8A0540; Tue, 13 Dec 2022 18:38:46 +0100 (CET) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 5B3DD40395; Tue, 13 Dec 2022 18:38:46 +0100 (CET) Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by mails.dpdk.org (Postfix) with ESMTP id 647EE4021D for ; Tue, 13 Dec 2022 18:38:44 +0100 (CET) Received: by linux.microsoft.com (Postfix, from userid 1086) id 9EFBD20B8775; Tue, 13 Dec 2022 09:38:43 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 9EFBD20B8775 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1670953123; bh=0O7xN6PVfG9+q6VqA+V2L+OrSXY58XhEGgYrNBD5LY4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Hq+R/CNXuzZZaKuYsiT0qL/gQkShuxMEcPGqUW61O/YQhzc9poYEs9GqJPBd6H/O1 uaxu+JC8P0iV0u3ikYBiT96fR+faWJbrZ7/MKiJ+IQZa3pUtibERcZHeM2WBy5+qQ3 lf1gmw6Uf2kbhfHlObFoJ7hOr2iNH7RiDkmv9zow= Date: Tue, 13 Dec 2022 09:38:43 -0800 From: Tyler Retzlaff To: Thomas Monjalon Cc: Stephen Hemminger , dev@dpdk.org, Morten =?iso-8859-1?Q?Br=F8rup?= , david.marchand@redhat.com, Bruce Richardson Subject: Re: help with pthread_t deprecation / api changes Message-ID: <20221213173843.GA8640@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> References: <20221130225427.GA13682@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> <14786965.JCcGWNJJiE@thomas> <20221212174544.GA27595@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> <5885133.UjTJXf6HLC@thomas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5885133.UjTJXf6HLC@thomas> 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, Dec 13, 2022 at 09:32:06AM +0100, Thomas Monjalon wrote: > 12/12/2022 18:45, Tyler Retzlaff: > > On Sun, Dec 11, 2022 at 08:50:48AM +0100, Thomas Monjalon wrote: > > > 10/12/2022 00:49, Tyler Retzlaff: > > > > On Fri, Dec 09, 2022 at 10:13:44PM +0100, Thomas Monjalon wrote: > > > > > 09/12/2022 21:06, Tyler Retzlaff: > > > > > > On Fri, Dec 09, 2022 at 08:48:14AM -0800, Stephen Hemminger wrote: > > > > > > > On Fri, 09 Dec 2022 08:53:57 +0100 > > > > > > > Thomas Monjalon wrote: > > > > > > > > > > > > > > > > > If some execution environment doesn't support thread names, it could return a string that makes it possible for a human to identify the thread, e.g. the tread id. Again, this is assuming that it is only used for debugging, trace, and similar. > > > > > > > > > > > > > > > > > > i think this raises a good question. is the purpose of setting a thread name > > > > > > > > > meant to be something we can use from the application or is it something that > > > > > > > > > is for debugging diagnostics and may be a best effort? > > > > > > > > > > > > > > > > > > > > > Thomas Monjalon wrote: > > > > > > > > > > > > > I think yes it is only for debugging. > > > > > > > So best effort looks to be a good approach. > > > > > > > I'm not sure you need to replace the functions. > > > > > > > Can you just complete the implementations? > > > > > > > > > > > > the patch series put forward allows a set / get name per-lcore, where > > > > > > you get implicit (but not exposed via the eal api) call to underlying > > > > > > platform thread setname. > > > > > > > > > > I don't understand how lcore ID and thread ID are connected. > > > > > You can run multiple control threads on a single lcore. > > > > > > > > > > > > > correct. > > > > > > > > the new public api allows the set of a name on an lcore only. as a > > > > side-effect if the platform supports it the name is also set on the > > > > thread_id associated with the lcore (from lcore_config[].thread_id). > > > > > > > > for control threads you just get the side-effect if the platform > > > > supports it, otherwise it is a noop. > > > > > > What does it mean? which side effect? what must be supported? > > > > > > > if we want set / get name at all this seemed the most usable balance > > > > between application consumption with debug use where available. if this > > > > isn't acceptable then i would suggest we simply remove both > > > > rte_thread_{get,set}name because as a debugging facility we cannot offer > > > > a consistent abstracted api which means it shouldn't be in the eal at > > > > all. > > > > > > Why it cannot be consistent? > > > Please be more precise. > > > > > > > sorry i thought you had been looking at our implementation, let me > > summarize. > > > > here are the differences between the underlying platform capabilities > > that prohibit both get and set. it's not a matter of just providing missing > > implementation for a specific platform. > > > > set thread name: > > freebsd > > - set reports no failure, but may silently fail > > - uncertain what name length limit is > > linux > > - set not available in older glibc > > - current rte wrapper silently truncates name length > > windows > > - set always available > > - uncertain what name length limit is > > > > get thread name: > > freebsd > > - not available at all > > linux > > - get not available in older glibc > > - get can fail > > windows > > - get always available > > - get can fail > > > > keep in mind the purpose of an abstraction is that the application *does > > not* have to do conditional evaluation on a per-platform basis around > > call sites. once you start putting #ifdef RTE_EXEC_ENV_XXX into code you > > failed and i presume we want none of the use of eal to be adorned with > > that. > > > > at first glance you might think oh, well if get isn't supported then > > just return some default string or an empty string but even that is a > > violation of the abstraction that leaks implementation detail. > > > > i.e. assuming success set() success get(set()) should also succeed > > without conditional compilation of the code. > > > > the common abstraction that can be reasonably provided explicitly > > operating a thread is something like. > > > > * for set you can provide a watered down version that doesn't report > > failure and silently truncates and ignores errors within the > > implementation. if it works it works if it doesn't you just don't > > know i.e. best effort. > > * for get it cannot be provided consistently, the platforms simply > > aren't providing what is needed. > > > > for background one of the request to expose the native platform thread > > id was to access the best effort behavior for the thread associated with > > an lcore. discussion on list highlighted the constraint that this should > > be done without exposing platform specific detail via the eal api. > > > > http://mails.dpdk.org/archives/dev/2022-October/253411.html > > > > as mentioned in a previous mail i provided a series that accomplishes > > this as a side effect of an api that can be consistently provided when > > available on the platform, it has 2 benefits. > > * it does not expose the platform-specific native thread handle. > > * for lcores it keeps the name in the application memory so it is > > available in crash/coredumps. > > > > so we have 2 options. > > > > 1. a watered down set (no get) that is fire and forget and reports no > > failure and maybe it works, maybe it doesn't depending on your platform. > > 2. the lcore set / get which is basically (1) for the threads associated > > with lcores but provides some additional features that are supportable > > in the api surface. (set/get, stored in application namespace). > > Given thread name is not critical at all, I think best effort is OK. > We could make clear in the API documentation that it is not reliable. > > I don't think implementing thread name in the specific case of > datapath lcore is a real improvement. Okay, just one final confirmation. This is what we would like? * completely remove the existing rte_thread_getname api. - by implication this means remove the 1 use of it in eal in logging. * introduce a new void rte_thread_set_name(rte_thread_t, const char *name) that: - returns void (does not fail), but in cases it can be detected will log a DEBUG level log message. - quietly truncates the name (if longer) to RTE_MAX_THREAD_NAME_LEN on all platforms. - document that it is best effort and only works if the stars align for the target platform. * there will be no unit test, since the set doesn't fail and there is no get to validate the set. once i get confirmation i'll update the series. thanks