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).
If you are able to reproduce this, can you try the following things : 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 2. Enable RCU_DEBUGGING options from config and get data points from those to see what is happening using ftrace. Thanks and regards, Vignesh Radhakrishnan On Wed, Jan 14, 2015 at 9:00 AM, meenakshi aggarwal <[email protected]> wrote: > Hi, > > > > > I am receiving following kernel warning while running kernel > > “3.12.19-rt30+ #6 SMP PREEMPT RT Tue Jan 13 15:35:39 IST 2015 armv7l > GNU/Linux” on ARM v7 platform. > > > > Kindly help. > > > > > > [ 1044.465822] libphy: mdio@2d24000:02 - Link is Up - 1000/Full > > [ 1058.805821] libphy: mdio@2d24000:00 - Link is Up - 1000/Full > > [ 1662.764689] ------------[ cut here ]------------ > > [ 1662.768867] WARNING: CPU: 1 PID: 18 at net/sched/sch_generic.c:279 > dev_watchdog+0x137/0x198() > > [ 1662.777581] NETDEV WATCHDOG: eth1 (fsl-gianfar): transmit queue 0 timed > out > > [ 1662.876129] Modules linked in: > > [ 1662.885557] CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 3.12.19-rt30+ > #1 > > [ 1662.885609] [<80010991>] (unwind_backtrace+0x1/0x88) from [<8000e677>] > (show_stack+0xb/0xc) > > [ 1662.885628] [<8000e677>] (show_stack+0xb/0xc) from [<803024d3>] > (dump_stack+0x4b/0x84) > > [ 1662.885646] [<803024d3>] (dump_stack+0x4b/0x84) from [<80018d4d>] > (warn_slowpath_common+0x45/0x64) > > [ 1662.885660] [<80018d4d>] (warn_slowpath_common+0x45/0x64) from > [<80018d87>] (warn_slowpath_fmt+0x1b/0x24) > > [ 1662.885678] [<80018d87>] (warn_slowpath_fmt+0x1b/0x24) from > [<8029e5b7>] (dev_watchdog+0x137/0x198) > > [ 1662.885697] [<8029e5b7>] (dev_watchdog+0x137/0x198) from [<8001fe53>] > (call_timer_fn.isra.32+0x17/0x54) > > [ 1662.885712] [<8001fe53>] (call_timer_fn.isra.32+0x17/0x54) from > [<8001ff97>] (run_timer_softirq+0x107/0x140) > > [ 1662.885725] [<8001ff97>] (run_timer_softirq+0x107/0x140) from > [<8001b7ad>] (do_current_softirqs+0x105/0x1cc) > > [ 1662.885737] [<8001b7ad>] (do_current_softirqs+0x105/0x1cc) from > [<8001b9cb>] (run_ksoftirqd+0x23/0x38) > > [ 1662.885754] [<8001b9cb>] (run_ksoftirqd+0x23/0x38) from [<8002fb15>] > (smpboot_thread_fn+0x175/0x188) > > [ 1662.885769] [<8002fb15>] (smpboot_thread_fn+0x175/0x188) from > [<8002a945>] (kthread+0x5d/0x6c) > > [ 1662.885784] [<8002a945>] (kthread+0x5d/0x6c) from [<8000c339>] > (ret_from_fork+0x11/0x38) > > [ 1662.893114] ---[ end trace 0000000000000002 ]--- > > [ 1682.685516] INFO: rcu_preempt detected stalls on CPUs/tasks: {} > (detected by 1, t=2102 jiffies, g=489, c=488, q=1155) > > [ 1682.685520] INFO: Stall ended before state dump start > > > > > Thanks & Regards > Meenakshi Aggarwal > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > -- http://vigneshradhakrishnan.blogspot.com/
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