From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36064) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SSDER-0003Ci-OT for qemu-devel@nongnu.org; Wed, 09 May 2012 16:11:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SSDEP-0003an-Q7 for qemu-devel@nongnu.org; Wed, 09 May 2012 16:11:31 -0400 Received: from goliath.siemens.de ([192.35.17.28]:29317) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SSDEP-0003aa-GO for qemu-devel@nongnu.org; Wed, 09 May 2012 16:11:29 -0400 Message-ID: <4FAACF69.50600@siemens.com> Date: Wed, 09 May 2012 17:11:21 -0300 From: Jan Kiszka MIME-Version: 1.0 References: <4FAAC3A3.5040503@siemens.com> <4FAAC521.5000907@msgid.tls.msk.ru> <4FAAC6B2.7040009@siemens.com> <4FAACA0A.5040602@us.ibm.com> <4FAACC0F.9080702@siemens.com> <4FAACD2F.30702@us.ibm.com> In-Reply-To: <4FAACD2F.30702@us.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1.1] coroutine: Avoid ucontext usage on i386 Linux host List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Kevin Wolf , Peter Maydell , Michael Tokarev , qemu-devel On 2012-05-09 17:01, Anthony Liguori wrote: > On 05/09/2012 02:57 PM, Jan Kiszka wrote: >> On 2012-05-09 16:48, Anthony Liguori wrote: >>> On 05/09/2012 02:34 PM, Jan Kiszka wrote: >>>>> Can't we resort to the SIGUSR1 workaround for the time being, while >>>>> no RT signals are in actual use, and just have the time to let the >>>>> kernel side to fix the things up before some actual RTsig user will >>>>> emerge in qemu? I think it is a bit more conservative approach, >>>>> especially having in mind the minority of users this issue affects >>>>> (only 32/64 mixed environment). I'd favor for this variant, and >>>>> it looks like I'm the "main" 32/64bit user of qemu in this world :) >>>> >>>> Most conservative is definitely this patch, not switching to SIGUSR1, >>>> hoping that no other RT signal user shows up until current kernel are no >>>> longer in use. >>> >>> Sorry, how is using a totally different code path more conservative than using a >>> different signal number? >> >> If the gthread version is not safe to use, why do we fall back to it? > > It's safe, but it's significantly slower. OK. Then what about sigaltstack (once fixed)? Is it also slower? If not, can we converge over it? I would really hate staying with this time bomb of broken RT signals unless someone tells me we will kick out all these coroutines rather sooner than later. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux