From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37363) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eop70-0002xD-Kv for qemu-devel@nongnu.org; Thu, 22 Feb 2018 06:32:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eop6z-0006ct-Rr for qemu-devel@nongnu.org; Thu, 22 Feb 2018 06:32:30 -0500 Date: Thu, 22 Feb 2018 12:32:04 +0100 From: Kevin Wolf Message-ID: <20180222113204.GC4147@localhost.localdomain> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37efa6ac-8e36-9c96-84ef-a8639ba64937@kamp.de> Subject: Re: [Qemu-devel] [Qemu-block] Limiting coroutine stack usage List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: Paolo Bonzini , qemu block , "qemu-devel@nongnu.org" , jsnow@redhat.com 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)) > Limiting the coroutine size to much could also lead to trouble in some > third party libraries that are called from a coroutine context, or > not? Yes, this is true. Kevin