Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964961AbVJUOlG (ORCPT ); Fri, 21 Oct 2005 10:41:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964962AbVJUOlG (ORCPT ); Fri, 21 Oct 2005 10:41:06 -0400 Received: from xproxy.gmail.com ([66.249.82.193]:24888 "EHLO xproxy.gmail.com") by vger.kernel.org with ESMTP id S964961AbVJUOlF convert rfc822-to-8bit (ORCPT ); Fri, 21 Oct 2005 10:41:05 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=dum1ubhHq4xEX5dPibgZgzRzCqqdi31v3vUFrQOPkXy8OCK7mIYJIcRRWKzEEvlfpKeNBBUQYwfQyQaIXiGfhU5g2AoB0iWpEJd+c3lIQWU+S1PsdU6ETR2tpyAs09fbbJ38cUIeVxJMfDxkR2SIzT+Vc+rwJh1p+5cZ0hL2W14= Message-ID: Date: Fri, 21 Oct 2005 16:41:04 +0200 From: Yitzchak Eidus To: Steven Rostedt Subject: Re: question about code from the linux kernel development ( se ) book Cc: linux-kernel@vger.kernel.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3087 Lines: 82 First Steve I want to thanks you for answering me your answered all the questions that i had I can understand your complains , and i will try to make it better next time ( i almost never used mailing lists... , so sorry about the white space striping , and the spelling... ) Jesper - yes it was a typo Nick - thanks :) On 10/21/05, Steven Rostedt wrote: > > Oh God, please indent code examples, and if your email client strips white > space, change your email client. > > On Fri, 21 Oct 2005, Yitzchak Eidus wrote: > > > first i am very sorry if it isnt the place to ask questions like this > > but i didnt know where else to ask ( i tryed irc channels and i was > > send from there to this list ) > > anyway: > > does this following code look buggy? : > > [ Indention added ] > > > DECLARE_WAITQUEUE ( wait , current ); > > add_wait_queue ( q , &wait ); > > while ( !condition ) { > > set_current_stat ( TASK_INTERRUPTABLE ); i > > if ( signal_pending ( current ) ) > > /* handle signal */ > > I assume that the signal_pending is the if result and not the schedule. > Since there was no indentation I couldn't tell. > > > schedule ( ); > /* Moved brace down added */ > } > > set_current_state ( TASK_RUNNING ); > > remove_wait_queue ( q , &wait ); > > Before I go to your questions, I'll first answer that this _is_ buggy > code. If the condition is checked and you are woken up between the > while (!condition) and the set_current_state, then you will end up > sleeping forever or until someone sends you a signal. > > > first:doesnt in the way from checking the !condition to > > set_current_state the condition can be changed no? > > Yes, and then put it again after schedule. > > > > > second:why not putting the schedule ( ); right after the > > set_current_state ( ) , what the point in checking the if ( > > signal_pending ( ) first, if the proccess doesnt started to sleep yet? > > Yes, I would put the signal_pending check after the schedule (as most of > the kernel does this). > > > third: in the cleaning in the way from putting the set_current_state ( > > TASK_RUNNING ) into remove_wait_queue , cant the queue wait list ( q ) > > wake up again the wait procsess? > > Yeah, so? There's no harm in that, except for an extra cpu cycles that > are done to wake it up. That, I wouldn't change. > > > ( thnks for the help , please if it can be done answer quickly i am > > tanker in the idf and need to come back to the army soon , ( no > > internet there... ) ) > > BTW, this is not an IRC, we use normal capitalization and normal spelling > (when we know how to spell a word ;-). So the next time you send to the > list, send it as if you were writing a serious letter, or you may just be > ignored. (as you might have been if I didn't respond). > > -- Steve > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/