From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39983) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eopFa-0006Pf-2Y for qemu-devel@nongnu.org; Thu, 22 Feb 2018 06:41:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eopFY-0002Aj-W0 for qemu-devel@nongnu.org; Thu, 22 Feb 2018 06:41:22 -0500 Date: Thu, 22 Feb 2018 11:40:53 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180222114053.GE9323@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <7b01ba4b-7f5f-30c7-d6d8-3c22f2774e7e@kamp.de> <7c23f28d-ee14-c504-ae13-04414c4b032e@redhat.com> <20180222105755.GB4147@localhost.localdomain> <37efa6ac-8e36-9c96-84ef-a8639ba64937@kamp.de> <20180222113204.GC4147@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180222113204.GC4147@localhost.localdomain> Subject: Re: [Qemu-devel] [Qemu-block] Limiting coroutine stack usage List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Peter Lieven , Paolo Bonzini , jsnow@redhat.com, "qemu-devel@nongnu.org" , qemu block On Thu, Feb 22, 2018 at 12:32:04PM +0100, Kevin Wolf wrote: > Am 22.02.2018 um 12:01 hat Peter Lieven geschrieben: > > Am 22.02.2018 um 11:57 schrieb Kevin Wolf: > > > Am 20.02.2018 um 22:54 hat Paolo Bonzini geschrieben: > > >> On 20/02/2018 18:04, Peter Lieven wrote: > > >>> Hi, > > >>> > > >>> I remember we discussed a long time ago to limit the stack usage of all > > >>> functions that are executed in a coroutine > > >>> context to a very low value to be able to safely limit the coroutine > > >>> stack size as well. > > >> IIRC the only issue was that hw/ide/atapi.c has mutual recursion between > > >> ide_atapi_cmd_reply_end -> ide_transfer_start -> ahci_start_transfer -> > > >> ide_atapi_cmd_reply_end. > > >> > > >> But perhaps it's not an issue, somebody needs to audit the code. > > > I think John intended to get rid of the recursion sometime, but I doubt > > > he has had the time so far. > > > > Apart from this is is possible to define special cflags in the > > Makefile.objs just for a subdirectory? I have patches ready to make > > the block layer files and other coroutine users compile with > > -Wstack-size=2048. But I do not want to specify each file separately. > > Our Makefiles have lines like this: > > iscsi.o-cflags := $(LIBISCSI_CFLAGS) > > I don't think there is a direct mechanism to apply cflags to a whole > directory or just to block-obj-y/block-obj-m, but just looping over them > could work. I'm not a Makefile expert at all, but after some toying with > a simple example, something like this might work: > > $(foreach x,$(block-obj-y),$(eval $x-cflags += -Wstack-size=2048)) You'll need it for anything block layer depends on too - so that's much of util/, crypto/ and io/ directories at least. So perhaps it would be shorter if we do the opposite - set -Wstack-size=2048 globally for everything in QEMU, and then override -Wstack-size=$BIGGER for the (hopefully) few sources that have a larger stack need ? Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|