From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 49BA4DDE31 for ; Tue, 24 Apr 2007 12:43:38 +1000 (EST) Subject: Re: [PATCH] powerpc pseries eeh: Convert to kthread API From: Benjamin Herrenschmidt To: "Eric W. Biederman" In-Reply-To: References: <11769695763104-git-send-email-ebiederm@xmission.com> <20070422123155.GF20763@infradead.org> <20070423205020.GR31947@austin.ibm.com> <1177378733.14873.52.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 24 Apr 2007 12:42:24 +1000 Message-Id: <1177382544.14873.57.camel@localhost.localdomain> Mime-Version: 1.0 Cc: ", linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , linuxppc-dev@ozlabs.org, Paul Mackerras , containers@lists.osdl.org, Oleg Nesterov List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2007-04-23 at 20:08 -0600, Eric W. Biederman wrote: > Benjamin Herrenschmidt writes: > > >> The only reason for using threads here is to get the error recovery > >> out of an interrupt context (where errors may be detected), and then, > >> an hour later, decrement a counter (which is how we limit these to > >> 6 per hour). Thread reaping is "trivial", the thread just exits > >> after an hour. > > > > In addition, it should be a thread and not done from within keventd > > because : > > > > - It can take a long time (well, relatively but still too long for a > > work queue) > > > > - The driver callbacks might need to use keventd or do flush_workqueue > > to synchronize with their own workqueues when doing an internal > > recovery. > > > >> Since these are events rare, I've no particular concern about > >> performance or resource consumption. The current code seems > >> to work just fine. :-) > > > > I think moving to kthread's is cleaner (just a wrapper around kernel > > threads that simplify dealing with reaping them out mostly) and I agree > > with Christoph that it would be nice to be able to "fire off" kthreads > > from interrupt context.. in many cases, we abuse work queues for things > > that should really done from kthreads instead (basically anything that > > takes more than a couple hundred microsecs or so). > > On that note does anyone have a problem is we manage the irq spawning > safe kthreads the same way that we manage the work queue entries. > > i.e. by a structure allocated by the caller? Not sure... I can see places where I might want to spawn an arbitrary number of these without having to preallocate structures... and if I allocate on the fly, then I need a way to free that structure when the kthread is reaped which I don't think we have currently, do we ? (In fact, I could use that for other things too now that I'm thinking of it ... I might have a go at providing optional kthread destructors). Ben.