how to check kernel is configured with preemption or not

how to check kernel is configured with preemption or not

[sri]

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?

Thanks inadvance.

-- Sri

-- 
--
 Krishna Mohan B
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how to check kernel is configured with preemption or not

[Daniel Baluta]

On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan@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?

how to check kernel is configured with preemption or not

[sri]

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@gmail.com>wrote:

> On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan@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?
>



-- 
--
 Krishna Mohan B
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how to check kernel is configured with preemption or not

[Greg Freemyer]

On Sun, Oct 23, 2011 at 1:34 PM, sri <bskmohan@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@gmail.com>
> wrote:
>>
>> On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan@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.

Remember /sys is part of the official ABI.

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.

Greg

how to check kernel is configured with preemption or not

[Greg KH]

On Sun, Oct 23, 2011 at 11:20:03PM -0400, Greg Freemyer wrote:
> On Sun, Oct 23, 2011 at 1:34 PM, sri <bskmohan@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@gmail.com>
> > wrote:
> >>
> >> On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan@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

how to check kernel is configured with preemption or not

[Sri Ram Vemulpali]

In your linux kernel code base say "make menuconfig"

goto "processor types and feature" in that you will find "preemption
model" option.
If you go to that option, you will find 3 traditional preemption
models, but if you have
preempt-rt patch is applied, then preempt-rt option will be given.
>From that you can know
whether your code base was applied with rt patch. And if it is
selected then, your bzImage is
rt linux.

If you want to test in real time, because you only have image, then
you can write normal
linux user space program using posix threads. From that you can
confirm whether it is
rt linux.

But you must get information whether this is rt linux by "uname -a",
it shows rt in the display of patch.

Thanks,
Sri.


On Mon, Oct 24, 2011 at 12:38 AM, Greg KH <greg@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@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@gmail.com>
>> > wrote:
>> >>
>> >> On Fri, Oct 21, 2011 at 2:28 PM, sri <bskmohan@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
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>



-- 
Regards,
Sri.

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@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@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@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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how to check kernel is configured with preemption or not

[Mulyadi Santosa]

Hi :)

On Thu, Oct 27, 2011 at 01:22, sri <bskmohan@gmail.com> wrote:
>
> 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.

IMHO, the problem here could be in fact showing that (if indeed it's
true) the related module has somekind of reentrancy problem...and
preemption in turn shows that to you or make it happen quicker.

A good written module should work fine no matter how many times it's
interrupted, assuming locks are used correctly in the critical
sections.


-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

how to check kernel is configured with preemption or not

[Greg KH]

On Wed, Oct 26, 2011 at 11:52:07PM +0530, sri wrote:
> 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).

That is a _very_ old kernel release, please use something more modern.

Anyway, this is a bug in the module you are using, there's not anything
that preempt vs. non-preempt that is handling this.  Please work with
the company providing the code to fix the bug in their driver.

greg k-h