On 02/25/2011 02:18 PM, Tejun Heo wrote:
Hello,
On Fri, Feb 25, 2011 at 12:46:16PM +0100, Dominik Klein wrote:
With 2.6.37 (also tried .1 and .2) it does not work but end up like I documented. With 2.6.38-rc1, it does work. With deadline scheduler, it also works in 2.6.37.
Okay, here's the problematic part.
<idle>-0 [013] 1640.975562: workqueue_queue_work: work struct=ffff88080f14f270 function=blk_throtl_work workqueue=ffff88102c8fc700 req_cpu=13 cpu=13 <idle>-0 [013] 1640.975564: workqueue_activate_work: work struct ffff88080f14f270 <...>-477 [013] 1640.975574: workqueue_execute_start: work struct ffff88080f14f270: function blk_throtl_work <idle>-0 [013] 1641.087450: workqueue_queue_work: work struct=ffff88080f14f270 function=blk_throtl_work workqueue=ffff88102c8fc700 req_cpu=13 cpu=13
The workqueue is per-cpu, so we only need to follow cpu=13 cases. @1640, blk_throtl_work() is queued, activated and starts executing but never finishes. The same work item is never executed more than once at the same on the same CPU, so when the next work item is queued, it doesn't get activated until the previous execution is complete.
The next thing to do would be finding out why blk_throtl_work() isn't finishing. sysrq-t or /proc/PID/stack should show us where it's stalled.
Thanks.
See attached logs of another run. sysctl -w kernel.sysrq=1 echo blk > /sys/kernel/debug/tracing/current_tracer echo 1 > /sys/block/sdb/trace/enable echo workqueue_queue_work >> /sys/kernel/debug/tracing/set_event echo workqueue_activate_work >> /sys/kernel/debug/tracing/set_event echo workqueue_execute_start >> /sys/kernel/debug/tracing/set_event echo workqueue_execute_end >> /sys/kernel/debug/tracing/set_event That makes attachment trace_pipe5.gz echo 8 > /proc/sysrq-trigger echo t > /proc/sysrq-trigger That makes attachment console.gz hth Dominik