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 itIf you are able to reproduce this, can you try the following things :
Vignesh Radhakrishnan
On Wed, Jan 14, 2015 at 9:00 AM, meenakshi aggarwal <meenu23688@xxxxxxxxx> 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 startThanks & RegardsMeenakshi Aggarwal
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