From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 19 Feb 2014 16:12:37 +0000 Subject: [PATCH v9 1/6] arm64: Add macros to manage processor debug state In-Reply-To: <20140219160359.GB22252@arm.com> References: <1390908022-10287-1-git-send-email-vijay.kilari@gmail.com> <1390908022-10287-2-git-send-email-vijay.kilari@gmail.com> <20140129105546.GC26622@mudshark.cambridge.arm.com> <20140217130149.GA5856@arm.com> <20140218120249.GD11049@arm.com> <20140219113157.GG30457@arm.com> <20140219160359.GB22252@arm.com> Message-ID: <20140219161236.GG28173@mudshark.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Feb 19, 2014 at 04:03:59PM +0000, Catalin Marinas wrote: > On Wed, Feb 19, 2014 at 11:31:57AM +0000, Catalin Marinas wrote: > > BUG: scheduling while atomic: kworker/u8:0/6/0x00000002 > > Modules linked in: > > CPU: 1 PID: 6 Comm: kworker/u8:0 Not tainted 3.14.0-rc3+ #306 > > Workqueue: khelper __call_usermodehelper > > Call trace: > > [] dump_backtrace+0x0/0x12c > > [] show_stack+0x14/0x1c > > [] dump_stack+0x78/0xc4 > > [] __schedule_bug+0x40/0x54 > > [] __schedule+0x514/0x604 > > [] schedule+0x28/0x78 > > [] schedule_timeout+0x170/0x1bc > > [] wait_for_common+0xc0/0x14c > > [] wait_for_completion_killable+0x14/0x28 > > [] do_fork+0x158/0x2a8 > > [] kernel_thread+0x30/0x38 > > [] __call_usermodehelper+0x34/0xa8 > > [] process_one_work+0x118/0x354 > > [] worker_thread+0x13c/0x3c0 > > [] kthread+0xd4/0xe8 > > > > > > It gets much worse if I run with two CPUs and CONFIG_KGDB_KDB enabled > > (but fine with a single CPU). > > > > So no need to post another series for now but please check the multi-CPU > > case as well and send a separate fix. I'll dig a bit on my side as well. > > So far I'm done with the investigation. It looks to me like one of the > kgdb tests, kgdb core or the arm64 back-end (or maybe more than one) is > not SMP safe. The errors either appear or disappear based on the printks > I put through the kgdb test or other config options which I enable. > > Could you please look into making the kgdb back-end SMP-safe? There are certainly potential SMP problems in the back-end, which I asked about in the initial series: http://lkml.kernel.org/r/CALicx6v1eGHRwWPrjzihzBZxCu8t1vpMoq-YfutSm4mRmP6gEQ at mail.gmail.com The reply from Vijay suggested that everything is confined to a single CPU. Will