2014-03-04 16:48 GMT-08:00 Eric Dumazet : > On Tue, 2014-03-04 at 15:55 -0800, Florian Fainelli wrote: >> Hi all, >> >> I am seeing the following RCU stalls messages appearing on an ARMv7 >> 4xCPUs system running 3.14-rc4: >> >> [ 42.974327] INFO: rcu_sched detected stalls on CPUs/tasks: >> [ 42.979839] (detected by 0, t=2102 jiffies, g=4294967082, >> c=4294967081, q=516) >> [ 42.987169] INFO: Stall ended before state dump start >> >> this is happening under the following conditions: >> >> - the attached bumper.c binary alters various kernel thread priorities >> based on the contents of bumpup.cfg and >> - malloc_crazy is running from a NFS share >> - malloc_crazy.c is running in a loop allocating chunks of memory but >> never freeing it >> >> when the priorities are altered, instead of getting the OOM killer to >> be invoked, the RCU stalls are happening. Taking NFS out of the >> equation does not allow me to reproduce the problem even with the >> priorities altered. >> >> This "problem" seems to have been there for quite a while now since I >> was able to get 3.8.13 to trigger that bug as well, with a slightly >> more detailed RCU debugging trace which points the finger at kswapd0. >> >> You should be able to get that reproduced under QEMU with the >> Versatile Express platform emulating a Cortex A15 CPU and the attached >> files. >> >> Any help or suggestions would be greatly appreciated. Thanks! > > Do you have a more complete trace, including stack traces ? Attatched is what I get out of SysRq-t, which is the only thing I have (note that the kernel is built with CONFIG_RCU_CPU_STALL_INFO=y): Thanks! -- Florian