On 03/04/2013 02:00 PM, Nathan Zimmer wrote: > Stephen Warren wrote at Monday, March 04, 2013 2:16 PM: >> On 02/15/2013 01:47 PM, Nathan Zimmer wrote: >>> I am currently tracking a hotlock reported by a customer on a large system, >>> 512 cores. I am currently running 3.8-rc7 but the issue looks like it has been >>> this way for a very long time. >>> The offending lock is proc_dir_entry->pde_unload_lock. >>> >>> This patch converts the replaces the lock with the rcu. However the pde_openers >>> list still is controlled by a spin lock. I tested on a 4096 machine and the lock >>> doesn't seem hot at least according to perf. >> >> Nathan, >> >> This patch causes RCU errors on my ARM systems (which have 2 or 4 CPUs) >> during boot; see the log below. Reverting it fixes the problem. Let me >> know if you need any more information to diagnose the problem. Thanks. > > I found and fixed a number of them, with the help of sparse. > http://marc.info/?l=linux-fsdevel&m=136242660212004&w=2 > If there are any I didn't find and fix let me know. Yes, if I revert the version of this patch that's in next-20130304, and replace it with V5 that you linked to above, then the problem is no longer present. Thanks. >> [ 3.652115] VFS: Mounted root (ext3 filesystem) on device 179:1. >> [ 3.664856] devtmpfs: mounted >> [ 3.668877] Freeing init memory: 212K > ... >> [ 25.765891] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=2102 jiffies, g=4294967050, c=4294967049, q=5749) >> [ 25.777786] INFO: Stall ended before state dump start >> [ 88.815886] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=8407 jiffies, g=4294967050, c=4294967049, q=5818) >> [ 88.827777] INFO: Stall ended before state dump start >> [ 151.865886] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=14712 jiffies, g=4294967050, c=4294967049, q=5869) >> [ 151.877863] INFO: Stall ended before state dump start >> [ 214.915885] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=21017 jiffies, g=4294967050, c=4294967049, q=5869) >> [ 214.927857] INFO: Stall ended before state dump start >> [ 240.525981] INFO: task mountall:71 blocked for more than 120 seconds. >> [ 240.532435] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 240.541452] INFO: task init:150 blocked for more than 120 seconds. >> [ 240.547687] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 240.556352] INFO: task udevd:151 blocked for more than 120 seconds. >> [ 240.562623] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 240.571262] INFO: task ata_id:197 blocked for more than 120 seconds. >> [ 240.577662] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 277.965881] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 0, t=27322 jiffies, g=4294967050, c=4294967049, q=5869) >> [ 277.977860] INFO: Stall ended before state dump start-- -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
