how to check kernel is configured with preemption or not

[sri]

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 <greg at kroah.com> wrote:

> On Sun, Oct 23, 2011 at 11:20:03PM -0400, Greg Freemyer wrote:
> > On Sun, Oct 23, 2011 at 1:34 PM, sri <bskmohan at gmail.com> wrote:
> > > 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>
> > > wrote:
> > >>
> > >> On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan at gmail.com> wrote:
> > >> > 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
> > >> > levels?
> > >>
> > >> Hmm, uname -a?
> > I'm sure its in /sys somewhere.
>
> I do not think so.
>
> > Remember /sys is part of the official ABI.
>
> As documented in Documentation/ABI/, so perhaps you can read there.
>
> > 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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