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Date: Fri, 26 Apr 2019 17:07:41 +0200 From: Heiko Carstens <heiko.carstens@...ibm.com> To: Prarit Bhargava <prarit@...hat.com> Cc: Jessica Yu <jeyu@...nel.org>, linux-next@...r.kernel.org, linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org, Cathy Avery <cavery@...hat.com> Subject: Re: [-next] system hangs likely due to "modules: Only return -EEXIST for modules that have finished loading" On Fri, Apr 26, 2019 at 09:22:34AM -0400, Prarit Bhargava wrote: > On 4/26/19 9:07 AM, Heiko Carstens wrote: > > Hello Prarit, > > > > it looks like your commit f9a75c1d717f ("modules: Only return -EEXIST > > for modules that have finished loading") _sometimes_ causes hangs on > > s390. This is unfortunately not 100% reproducible, however the > > mentioned commit seems to be the only relevant one in modules.c. > > > > What I see is a hanging system with messages like this on the console: > > > > [ 65.876040] rcu: INFO: rcu_sched self-detected stall on CPU > > [ 65.876049] rcu: 7-....: (5999 ticks this GP) idle=eae/1/0x4000000000000002 softirq=1181/1181 fqs=2729 > > [ 65.876078] (t=6000 jiffies g=-471 q=17196) > > [ 65.876084] Task dump for CPU 7: > > [ 65.876088] systemd-udevd R running task 0 731 721 0x06000004 > > [ 65.876097] Call Trace: > > [ 65.876113] ([<0000000000abb264>] __schedule+0x2e4/0x6e0) > > [ 65.876122] [<00000000001ee486>] finished_loading+0x4e/0xb0 > > [ 65.876128] [<00000000001f1ed6>] load_module+0xcce/0x27a0 > > [ 65.876134] [<00000000001f3af0>] __s390x_sys_init_module+0x148/0x178 > > [ 65.876142] [<0000000000ac0766>] system_call+0x2aa/0x2c8 > > I did not look any further into the dump, however since the commit > > touches exactly the code path which seems to be looping... ;) > > > > Ouch :( I wonder if I exposed a further race or another bug. Heiko, can you > determine which module is stuck? Warning: I have not compiled this code. Here we go: [ 11.716866] PRARIT: waiting for module s390_trng to load. [ 11.716867] PRARIT: waiting for module s390_trng to load. [ 11.716868] PRARIT: waiting for module s390_trng to load. [ 11.716870] PRARIT: waiting for module s390_trng to load. [ 11.716871] PRARIT: waiting for module s390_trng to load. [ 11.716872] PRARIT: waiting for module s390_trng to load. [ 11.716874] PRARIT: waiting for module s390_trng to load. [ 11.716875] PRARIT: waiting for module s390_trng to load. [ 11.716876] PRARIT: waiting for module s390_trng to load. [ 16.726850] add_unformed_module: 31403529 callbacks suppressed [ 16.726853] PRARIT: waiting for module s390_trng to load. [ 16.726862] PRARIT: waiting for module s390_trng to load. [ 16.726865] PRARIT: waiting for module s390_trng to load. [ 16.726867] PRARIT: waiting for module s390_trng to load. [ 16.726869] PRARIT: waiting for module s390_trng to load. If I'm not mistaken then there was _no_ corresponding message on the console stating that the module already exists.
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