Re: Question on Schedule and Preemption

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

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).

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?

===================================
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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