Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-12

[Fernando Lopez-Lezcano]

On Sat, 2004-12-11 at 04:30, Steven Rostedt wrote:
> On Fri, 2004-12-10 at 23:37 -0800, Fernando Lopez-Lezcano wrote:
> > Can't wait to try the patch, I don't have CONFI_PCI_MSI defined in the
> > configurations I use. I've had problems with a network card (R8169
> > driver) for a while (I think I reported it), the interrupts were being
> > ignored. Hopefully the same problem...
>
> You may have the same problem but the patch I sent won't solve it.  My
> patch only is a problem if you have CONFIG_PCI_MSI defined. But I'm sure
> there exists other instances that threading hardirqs might not work
> properly with other configurations. Send me your .config, and if I get
> time I'll take a look. (also your /proc/cpuinfo might help).
> 
> Before you send this, make sure that it is the hardirqs that's the
> problem. Switch to PREEMPT_DESKTOP and make sure hardirqs are not
> threaded.

[The following is all done booting into 0.7.32-19, interrupt scheduling
and priorities unchanged from the defaults]

I'm using PREEMPT_DESKTOP. I don't know how to force the kernel to not
thread hardirqs. What I did (maybe the same thing?) is to boot single
user, then turn off /proc/sys/kernel/hardirq_preempt, and then start the
network. It works (the network). And then I tried the same thing with
hardirq_preempt=1 and still worked when booting single user... :-(

So, these are the interrupts after booting single user:
           CPU0       
  0:      36426    IO-APIC-edge  timer  0/35956
  1:        143    IO-APIC-edge  i8042  0/143
  4:          0    IO-APIC-edge  KGDB-stub  0/0
  8:          1    IO-APIC-edge  rtc  0/1
  9:          0   IO-APIC-level  acpi  0/0
 12:        100    IO-APIC-edge  i8042  0/100
 14:         26    IO-APIC-edge  ide0  1/24
 17:         59   IO-APIC-level  libata, libata  0/59
 20:       1462   IO-APIC-level  libata  0/1462
 21:          0   IO-APIC-level  ehci_hcd, uhci_hcd, uhci_hcd, uhci_hcd,
uhci_hcd  0/0
NMI:       7544 
LOC:      36254 
ERR:          0
MIS:          0

Here's the extra one I have after I start the network

 16:          7   IO-APIC-level  eth0  0/7

(network works). I then telinit 3, no changes in interrupts (except for
the count numbers), network continues working. 

I then telinit 5 and the network dies. This is the added interrupt:

 11:          0    IO-APIC-edge  radeon@PCI:1:0:0  0/0

I tried repeating the whole thing but going through all the services in
the transition from level 3 to level 5 one by one, and nothing happened
to the network so it must be X. I then rebooted into single user,
started the network and loaded the radeon kernel module alone and the
network was not affected. 

So, this is what I get in dmesg when I go into level 5:

NET: Registered protocol family 10
Disabled Privacy Extensions on device c03e0ec0(lo)
IPv6 over IPv4 tunneling driver
divert: not allocating divert_blk for non-ethernet device sit0
eth0: no IPv6 routers present
[drm] Initialized radeon 1.11.0 20020828 on minor 0:
ACPI: PCI interrupt 0000:01:00.0[A] -> GSI 16 (level, low) -> IRQ 16
agpgart: Found an AGP 3.0 compliant device at 0000:00:00.0.
agpgart: Putting AGP V3 device at 0000:00:00.0 into 4x mode
agpgart: Putting AGP V3 device at 0000:01:00.0 into 4x mode
[drm] Loading R200 Microcode
irq 16: nobody cared!
 [<c01041e3>] dump_stack+0x23/0x30 (20)
 [<c014d480>] __report_bad_irq+0x30/0xa0 (24)
 [<c014d590>] note_interrupt+0x70/0xb0 (32)
 [<c014d30c>] do_hardirq+0x13c/0x150 (40)
 [<c014d399>] do_irqd+0x79/0xb0 (32)
 [<c013bf7a>] kthread+0xaa/0xb0 (48)
 [<c0101335>] kernel_thread_helper+0x5/0x10 (153411604)
---------------------------
| preempt count: 00000002 ]
| 2-level deep critical section nesting:
----------------------------------------
.. [<c014d2aa>] .... do_hardirq+0xda/0x150
.....[<c014d399>] ..   ( <= do_irqd+0x79/0xb0)
.. [<c014045d>] .... print_traces+0x1d/0x60
.....[<c01041e3>] ..   ( <= dump_stack+0x23/0x30)
 
handlers:
[<f88e3f00>] (rtl8169_interrupt+0x0/0x1a0 [r8169])
Disabling IRQ #16

Anything else I could test?

> If the problem goes away, then this may be your problem. If
> it does not, I'm afraid that it's something else, and you don't need to
> send me anything.

Let me know if you still want the .config...
-- Fernando


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