Am working on a problem where the system hanging after some unequal
intervals, with the below o/p printing on the console,
Though this might be mostly tighten to the click router module am using, but
I see the do_IRQ in the stack trace multiple times.
This brought some suspicious questions to me why so many times the module is
interrupted.
Ealier I was running with centos5.3 kernel, now running with centos5.5
kernel (2.6.18-194).
In the new kernel config, I found CONFIG_PREPEMPT_NONE=y and
CONFIG_PREEMPT_VOLUNTARY is not set, whereas these options are opposite in
the old kernel.

This made to look for what preemption level the kernel is running with?
=======================
low stack detected by irq handler
[<c0405e9b>] do_IRQ+0x86/0xc3
[<c04046e6>] common_interrupt+0x1a/0x20
[<c05b83c6>] __ip_route_output_key+0x774/0x79e
[<fb817e32>] _ZN8FromHost5fl_txEP7sk_buffP10net_device+0xc2/0x100 [click]
[<c05a1b23>] dev_hard_start_xmit+0x1b4/0x25a
[<c05af12f>] __qdisc_run+0xd6/0x153
[<c05a3196>] dev_queue_xmit+0x1f8/0x216
[<c05a7431>] neigh_resolve_output+0x170/0x19a
[<c05b8403>] ip_route_output_flow+0x13/0x1d4
[<c05bd2db>] ip_push_pending_frames+0x31a/0x3a4
[<c05b85cd>] ip_route_output_key+0x9/0xb
[<c05bdd5d>] ip_send_reply+0xf8/0x209
[<c0418baf>] __wake_up+0x11/0x1a
[<c059b077>] sock_def_readable+0x26/0x4b
[<c05c9cf4>] tcp_data_queue+0x4c7/0x9a4
[<c05cfc56>] tcp_v4_send_reset+0x104/0x11c
[<c05d0879>] tcp_v4_do_rcv+0x240/0x269
[<c05d28cb>] tcp_v4_rcv+0x7f7/0x848
[<c05bb173>] ip_local_deliver+0x157/0x1d0
[<c05baff2>] ip_rcv+0x3cb/0x3f5
[<c05a141d>] __netif_receive_skb+0x3b3/0x3d5
[<fb81c21e>] _ZN6ToHost4pushEiP6Packet+0xee/0x210 [click]
[<fb83985d>] _ZN12EnsureEther24pushEiP6Packet+0x1d/0x20 [click]
[<fb82b895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click]
[<c05bb173>] ip_local_deliver+0x157/0x1d0
[<c043f334>] __do_IRQ+0x0/0x9f
[<c0405ecc>] do_IRQ+0xb7/0xc3
[<c04046e6>] common_interrupt+0x1a/0x20
[<fb80942d>] _ZN4IPRw7Mapping9make_pairEiRK8IPFlowIDS3_iiPS0_S4_+0xad/0xd0
[click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb86679e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click]
[<fb80acfb>]
_ZN4IPRw7Pattern14create_mappingEiRK8IPFlowIDiiPNS_7MappingES5_RK7HashMapIS1_S5_E+0x1cb/0x1f0
[click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb86679e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click]
[<fb883ce3>]
_ZN10IPRewriter13apply_patternEPN4IPRw7PatternEiRK8IPFlowIDii+0x153/0x160
[click]
[<fb883d9e>] _ZN10IPRewriter4pushEiP6Packet+0xae/0x260 [click]
[<fb855535>] _ZN11MacThrottle10l2PushProcEiP6Packet+0x55/0x3b0 [click]
[<fb82b895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click]
[<c04046e6>] common_interrupt+0x1a/0x20
[<c05a007b>] dev_seq_next+0xc/0x16
[<fb82b895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click]
[<c05bf06c>] ip_queue_xmit+0x3cb/0x401
[<c05a3196>] dev_queue_xmit+0x1f8/0x216
[<fb855b96>] _ZN11MacThrottle4pushEiP6Packet+0x306/0x1890 [click]
[<c05bf06c>] ip_queue_xmit+0x3cb/0x401
[<c0417f22>] enqueue_task+0x29/0x39
[<c043f334>] __do_IRQ+0x0/0x9f
[<c0405ecc>] do_IRQ+0xb7/0xc3
[<c04046e6>] common_interrupt+0x1a/0x20
[<fb7c0806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb7c0806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb859075>] _ZN17NtlmLoginDetector4pushEiP6Packet+0x65/0x15d0 [click]
[<fb88a881>] _ZN15RecycledSkbPool7recycleEP7sk_buff+0x31/0xf0 [click]
[<fb866fdb>] _ZN14PerfigoDiscard4pushEiP6Packet+0x4b/0x1c0 [click]
[<c0411f41>] smp_apic_timer_interrupt+0x32/0x45
[<c05bb173>] ip_local_deliver+0x157/0x1d0
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb843e86>] _ZN11HashIPTable4pushEiP6Packet+0xf6/0x2d0 [click]
[<fb86679e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click]
[<fb81c21e>] _ZN6ToHost4pushEiP6Packet+0xee/0x210 [click]
[<fb7fd904>] _ZN8IPFilter4pushEiP6Packet+0x64/0xf0 [click]
[<fb84f517>] _ZN12IPPortLookup4pushEiP6Packet+0x47/0x9e0 [click]
[<fb7bca6f>] _ZN6Packet19expensive_uniqueifyEiib+0x18f/0x1c0 [click]
[<fb8385fc>] _ZN10DnsHandler17is_packet_allowedEPK6Packeti+0x8c/0x5e0
[click]
[<fb8319d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click]
[<fb8319d8>] _ZN8BWShaper4pushEiP6Packet+0x58/0xe90 [click]
[<fb8333a0>]
_ZN10DnsHandler15is_host_matchedERK6VectorINS_9HostEntryEERK6StringRb+0x90/0x150
[click]
[<fb833753>]
_ZN10DnsHandler13get_dns_queryEPKcS1_RS1_R17perfigo_dns_queryR6String+0x43/0x90
[click]
[<fb838bb8>] _ZN10DnsHandler4pushEiP6Packet+0x68/0xb00 [click]
[<fb835593>] _ZN10DnsHandler17process_dns_replyEPK6Packet+0x493/0x860
[click]
[<fb82b67b>] _ZN11ARPQuerier44pushEiP6Packet+0x2ab/0x2370 [click]
[<fb838bb8>] _ZN10DnsHandler4pushEiP6Packet+0x68/0xb00 [click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb84d34f>] _ZN13IPFilterGroup4pushEiP6Packet+0x19f/0xa80 [click]
[<fb81c21e>] _ZN6ToHost4pushEiP6Packet+0xee/0x210 [click]
[<fb7bcb42>] _ZN6Packet4makeEjPKhjj+0x32/0x100 [click]
[<fb83985d>] _ZN12EnsureEther24pushEiP6Packet+0x1d/0x20 [click]
[<fb82b895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click]
[<c043f334>] __do_IRQ+0x0/0x9f
[<c0405ecc>] do_IRQ+0xb7/0xc3
[<fb83e492>] _ZN13HashIPLookup34pushEiP6Packet+0x112/0x1c0 [click]
[<fb8516cf>] _ZN15LinearIPFilter24pushEiP6Packet+0x4f/0x3f0 [click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<fb80c1d1>] _ZN14LinearIPLookup4pushEiP6Packet+0x71/0x100 [click]
[<fb829a94>] _ZN11ARPQuerier49handle_ipEP6Packet+0x734/0xe30 [click]
[<fb848289>] _ZN14HashMACLookup54pushEiP6Packet+0x249/0x890 [click]
[<fb86679e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click]
[<c0417f22>] enqueue_task+0x29/0x39
[<c05c0000>] ip_setsockopt+0x184/0xa03
[<fb83f5b7>] _ZN13HashIPLookup54pushEiP6Packet+0xc7/0x110 [click]
[<fb8516cf>] _ZN15LinearIPFilter24pushEiP6Packet+0x4f/0x3f0 [click]
[<fb7fd904>] _ZN8IPFilter4pushEiP6Packet+0x64/0xf0 [click]
[<fb869516>] _ZN10Classifier4pushEiP6Packet+0x76/0xe0 [click]
[<fb84262e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click]
[<fb84262e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click]
[<fb82b67b>] _ZN11ARPQuerier44pushEiP6Packet+0x2ab/0x2370 [click]
[<c05d28cb>] tcp_v4_rcv+0x7f7/0x848
[<fb82ab12>] _ZN11ARPQuerier415handle_responseEP6Packet+0x32/0x8f0 [click]
[<fb84857a>] _ZN14HashMACLookup54pushEiP6Packet+0x53a/0x890 [click]
[<fb7fd904>] _ZN8IPFilter4pushEiP6Packet+0x64/0xf0 [click]
[<fb82b895>] _ZN11ARPQuerier44pushEiP6Packet+0x4c5/0x2370 [click]
[<c05a141d>] __netif_receive_skb+0x3b3/0x3d5
[<fb883d9e>] _ZN10IPRewriter4pushEiP6Packet+0xae/0x260 [click]
[<fb84262e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click]
[<fb86679e>] _ZN6Passer4pushEiP6Packet+0x12e/0x860 [click]
[<fb84262e>] _ZN12HashIPTable24pushEiP6Packet+0x18e/0x580 [click]
[<fb872674>] _ZN11PaintSwitch4pushEiP6Packet+0x44/0xe0 [click]
[<c05a141d>] __netif_receive_skb+0x3b3/0x3d5
[<c043f334>] __do_IRQ+0x0/0x9f
[<c0405ecc>] do_IRQ+0xb7/0xc3
[<c043f334>] __do_IRQ+0x0/0x9f
[<c0405ecc>] do_IRQ+0xb7/0xc3
[<fb869516>] _ZN10Classifier4pushEiP6Packet+0x76/0xe0 [click]
[<fb7c0806>] _ZN7Element4pushEiP6Packet+0x26/0x40 [click]
[<fb8162a5>] _ZN10FromDevice8run_taskEP4Task+0xa5/0x120 [click]
[<fb7d7127>] _ZN12RouterThread6driverEv+0x177/0x290 [click]
[<fb887822>] _Z11click_schedPv+0x82/0x130 [click]
[<fb8877a0>] _Z11click_schedPv+0x0/0x130 [click]
[<c0404987>] kernel_thread_helper+0x7/0x10

--Sri


On Mon, Oct 24, 2011 at 10:08 AM, Greg KH [off-list ref] wrote:

On Sun, Oct 23, 2011 at 11:20:03PM -0400, Greg Freemyer wrote:

quoted

On Sun, Oct 23, 2011 at 1:34 PM, sri [off-list ref] wrote:

quoted

No, uname did not show anything.
Is there any way to get the kernel preemption mode, programatically?

Thanks,
--Sri

On Fri, Oct 21, 2011 at 6:41 PM, Daniel Baluta <

daniel.baluta at gmail.com>

quoted

quoted

wrote:

quoted

On Fri, Oct 21, 2011 at 2:28 PM, sri [off-list ref] wrote:

quoted

Hi,

Am using kernel 2.6.18-195(centos 5.5).
My kernel configs have CONFIG_PREEMPT_NONE=7 and
"CONFIG_PREEMPT_VOLUNTERY
is not set".
How to check that preemption is really in place?
Is there any way to check my kernel is configured with what

preemption

quoted

quoted

quoted

quoted

levels?

Hmm, uname -a?

I'm sure its in /sys somewhere.

I do not think so.

quoted

Remember /sys is part of the official ABI.

As documented in Documentation/ABI/, so perhaps you can read there.

quoted

Also, you see what your config look like for sure by looking at
/proc/config.gz  (that file is virtual, but shows the contents of how
your config file was at compile time for the running kernel.

Not all distros enable this :(

I think the question needs to really be stated, why, from userspace,
does it matter if preempt is enabled or not?  This should never be
something that userspace cares about at all.

greg k-h

-- 
--
 Krishna Mohan B
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