<div dir="ltr"><div><div><div>This seems to have hit RCU stalls here which got solved while detecting this. This happens when a grace period is not completed for more than 21 seconds (modifiable timeout from config). <br><br>If you are able to reproduce this, can you try the following things :<br><br></div>1. Enable lockdep and use debug_show_all_locks() API inside the stall detection code to see who are holding the read locks and figure out why they are not releasing it<br></div>2. Enable RCU_DEBUGGING options from config and get data points from those to see what is happening using ftrace.<br><br></div>Thanks and regards,<br>Vignesh Radhakrishnan<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jan 14, 2015 at 9:00 AM, meenakshi aggarwal <span dir="ltr"><<a href="mailto:meenu23688@gmail.com" target="_blank">meenu23688@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi,<br><br> <br> <br><br>I am receiving following kernel warning while running kernel<br><br>“3.12.19-rt30+ #6 SMP PREEMPT RT Tue Jan 13 15:35:39 IST 2015 armv7l GNU/Linux” on ARM v7 platform.<br><br> <br><br>Kindly help.<br><br> <br><br> <br><br>[ 1044.465822] libphy: mdio@2d24000:02 - Link is Up - 1000/Full<br><br>[ 1058.805821] libphy: mdio@2d24000:00 - Link is Up - 1000/Full<br><br>[ 1662.764689] ------------[ cut here ]------------<br><br>[ 1662.768867] WARNING: CPU: 1 PID: 18 at net/sched/sch_generic.c:279 dev_watchdog+0x137/0x198()<br><br>[ 1662.777581] NETDEV WATCHDOG: eth1 (fsl-gianfar): transmit queue 0 timed out<br><br>[ 1662.876129] Modules linked in:<br><br>[ 1662.885557] CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 3.12.19-rt30+ #1<br><br>[ 1662.885609] [<80010991>] (unwind_backtrace+0x1/0x88) from [<8000e677>] (show_stack+0xb/0xc)<br><br>[ 1662.885628] [<8000e677>] (show_stack+0xb/0xc) from [<803024d3>] (dump_stack+0x4b/0x84)<br><br>[ 1662.885646] [<803024d3>] (dump_stack+0x4b/0x84) from [<80018d4d>] (warn_slowpath_common+0x45/0x64)<br><br>[ 1662.885660] [<80018d4d>] (warn_slowpath_common+0x45/0x64) from [<80018d87>] (warn_slowpath_fmt+0x1b/0x24)<br><br>[ 1662.885678] [<80018d87>] (warn_slowpath_fmt+0x1b/0x24) from [<8029e5b7>] (dev_watchdog+0x137/0x198)<br><br>[ 1662.885697] [<8029e5b7>] (dev_watchdog+0x137/0x198) from [<8001fe53>] (call_timer_fn.isra.32+0x17/0x54)<br><br>[ 1662.885712] [<8001fe53>] (call_timer_fn.isra.32+0x17/0x54) from [<8001ff97>] (run_timer_softirq+0x107/0x140)<br><br>[ 1662.885725] [<8001ff97>] (run_timer_softirq+0x107/0x140) from [<8001b7ad>] (do_current_softirqs+0x105/0x1cc)<br><br>[ 1662.885737] [<8001b7ad>] (do_current_softirqs+0x105/0x1cc) from [<8001b9cb>] (run_ksoftirqd+0x23/0x38)<br><br>[ 1662.885754] [<8001b9cb>] (run_ksoftirqd+0x23/0x38) from [<8002fb15>] (smpboot_thread_fn+0x175/0x188)<br><br>[ 1662.885769] [<8002fb15>] (smpboot_thread_fn+0x175/0x188) from [<8002a945>] (kthread+0x5d/0x6c)<br><br>[ 1662.885784] [<8002a945>] (kthread+0x5d/0x6c) from [<8000c339>] (ret_from_fork+0x11/0x38)<br><br>[ 1662.893114] ---[ end trace 0000000000000002 ]---<br><br>[ 1682.685516] INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=2102 jiffies, g=489, c=488, q=1155)<br><br>[ 1682.685520] INFO: Stall ended before state dump start<div><br></div><div><br></div><div><br></div><div><br></div><div>Thanks & Regards</div><span class="HOEnZb"><font color="#888888"><div>Meenakshi Aggarwal</div></font></span></div>
<br>_______________________________________________<br>
Kernelnewbies mailing list<br>
<a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br>
<a href="http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies" target="_blank">http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies</a><br>
<br></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature"><a href="http://vigneshradhakrishnan.blogspot.com/" target="_blank">http://vigneshradhakrishnan.blogspot.com/</a><br></div>
</div>