Re: Question on Schedule and Preemption

["Liu haixiang" <liu.haixiang@gmail.com>]

2006/4/18, Steven Rostedt <rostedt@kihontech.com>:
> On Tue, 2006-04-18 at 20:55 +0800, Liu haixiang wrote:
> > Hi Andreas Mohr,
> >
> > Thanks for your explanation. And now I am clear on above code.
> >
> > Please see my problem below. It seemed that there is one code to add
> > preempt count [<8440de20>], which means that the kernel can not be
> > preemptied. Then the code call switch_to (which contains the code
> > __switch_to_end).
>
> Your stack trace looks fishy, I recommend doing a "make menuconfig", go
> to "Kernel Hacking" and turn on "Compile the kernel with frame pointers"
> This will give you a better and cleaner stack dump.
>

Thank  you. And I will try it later.

> >
> > And it's problem becuase the code already in the atomic status and can
> > not be scheduled.
> >
> > My understanding is correct? And how to know which process or code
> > call add_preempt_count? Is there any good way to find the clue?
>
> Well according to your output, it was the task "TURNER0" with the pid
> 611.  After you recompile the kernel with CONFIG_FRAME_POINTERS you will
> need to follow the stack trace and see what function turned off
> preemption.  This can happen calling a spin_lock and not unlocking it
> before calling something that would schedule.
>

If it's true, it is a great help for me.

> If you also turn on in "Kernel Hacking" -> "Compile the kernel with
> debug info", you can then do a "gdb vmlinux" in the root directory of
> the compile, and pass in the stack address with the command
> "li *0xc042382e" to show where that function would return. (replace the
> c042382e with the location you are looking for).
>
> Also, what arch are you using to get a 0x04000000 in the preempt_count
> (the 0x1 is the depth). Of course I'm looking at 2.6.17-rc1 and not the
> one you are using.  Hmm, your arch may not even support frame pointers.
>
> -- Steve
>

The arch is SH4.

> >
> > ===================================
> > scheduling while atomic: TUNER0/0x04000001/611
> >
> > Call trace:
> > [<846532b4>] __switch_to_end+0x2fe/0x38a
> > [<8440de20>] add_preempt_count+0x0/0xa0
> > [<84652c80>] schedule+0x0/0x300
> > [<8440dd80>] sub_preempt_count+0x0/0xa0
> > [<84653ef8>] cond_resched+0x38/0x80
> > [<84405096>] ret_from_irq+0x0/0x12
> > [<845145e0>] __delay+0x0/0x20
> > [<84653ef8>] cond_resched+0x38/0x80
> > [<8440de20>] add_preempt_count+0x0/0xa0
> > [<84652c80>] schedule+0x0/0x300
> > [<8440dd80>] sub_preempt_count+0x0/0xa0
> > [<845d9a16>] bit_xfer+0x256/0x8c0
> > [<845d6d36>] i2c_transfer+0x56/0xe0
> > [<c042382e>] STI2C_Read+0x2e/0x80 [sti2c_ioctl]
> > [<c046af32>] I2C_ReadWrite+0x72/0x1a0 [sttuner_core]
> > [<c0487d7c>] IOARCH_Handle+0x10/0xffff49a0 [sttuner_core]
> > [<84653ec0>] cond_resched+0x0/0x80
> > [<845d9cac>] bit_xfer+0x4ec/0x8c0
> > [<c046b398>] IOARCH_ReadWrite+0x118/0x180 [sttuner_core]
> > [<c05cb000>] 0xc05cb000
> > [<c046b456>] STTUNER_IOARCH_ReadWrite+0x16/0x40 [sttuner_core]
> > [<c05c300c>] 0xc05c300c
> > [<c0477482>] STTUNER_IOREG_GetContigousRegisters+0x142/0x1c0 [sttuner_core]
> > [<c046fd1a>] Drv0299_GetNoiseEstimator+0x1a/0x120 [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c0483798>] STTUNER_DrvInst+0x1a8/0xffff911c [sttuner_core]
> > [<c048379c>] STTUNER_DrvInst+0x1ac/0xffff911c [sttuner_core]
> > [<c048379c>] STTUNER_DrvInst+0x1ac/0xffff911c [sttuner_core]
> > [<c05c300c>] 0xc05c300c
> > [<c05c3000>] 0xc05c3000
> > [<c0470960>] demod_d0299_GetSignalQuality+0x20/0x40 [sttuner_core]
> > [<c048379c>] STTUNER_DrvInst+0x1ac/0xffff911c [sttuner_core]
> > [<c0483798>] STTUNER_DrvInst+0x1a8/0xffff911c [sttuner_core]
> > [<c05c3000>] 0xc05c3000
> > [<c046c826>] SATTASK_GetTunerInfo+0x46/0xe0 [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c04837ac>] STTUNER_DrvInst+0x1bc/0xffff911c [sttuner_core]
> > [<c046c9fa>] SATTASK_ProcessTracking+0x13a/0x1c0 [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c046d388>] SATTASK_ScanTask+0x3e8/0x620 [sttuner_core]
> > [<c046ca80>] SATTASK_ProcessScanExact+0x0/0x340 [sttuner_core]
> > [<c0483800>] STTUNER_DrvInst+0x210/0xffff911c [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c048482c>] STTUNER_DrvInst+0x123c/0xffff911c [sttuner_core]
> > [<c048492c>] STTUNER_DrvInst+0x133c/0xffff911c [sttuner_core]
> > [<c04835f0>] STTUNER_DrvInst+0x0/0xffff911c [sttuner_core]
> > [<c04836ec>] STTUNER_DrvInst+0xfc/0xffff911c [sttuner_core]
> > [<c04836ec>] STTUNER_DrvInst+0xfc/0xffff911c [sttuner_core]
> > [<c04848ec>] STTUNER_DrvInst+0x12fc/0xffff911c [sttuner_core]
> > [<c04848ec>] STTUNER_DrvInst+0x12fc/0xffff911c [sttuner_core]
> > [<c048492c>] STTUNER_DrvInst+0x133c/0xffff911c [sttuner_core]
> > [<8442b4e4>] kthread+0xe4/0x140
> > [<c046cfa0>] SATTASK_ScanTask+0x0/0x620 [sttuner_core]
> > [<c0483800>] STTUNER_DrvInst+0x210/0xffff911c [sttuner_core]
> > [<8440f4a0>] complete+0x0/0xc0
> > [<8442b3e0>] kthread_should_stop+0x0/0x20
> > [<84403004>] kernel_thread_helper+0x4/0x20
> > -
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> --
> Steven Rostedt
> Senior Programmer
> Kihon Technologies
> (607)786-4830
>
>
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