Anders Blomdell wrote:
On a PrPMC800 (PPC 7410 processor) withe Xenomai-2.1-rc2, I get the following if the interrupt handler takes too long (i.e. next interrupt gets generated before the previous one has finished)


[   42.543765]  [c00c2008] spin_bug+0xa8/0xc4
[   42.597617]  [c00c22d4] _raw_spin_lock+0x180/0x184

Someone (in arch/ppc64/kernel/*.c?) is spinlocking+irqsave desc->lock for any given IRQ without using the Adeos *_hw() spinlock variant that masks the interrupt at hw level. So we seem to have:

spin_lock_irqsave(&desc->lock)
        <hw IRQ>
                __ipipe_grab_irq
                        __ipipe_handle_irq
                                __ipipe_ack_irq
                                        spin_lock...(&desc->lock)
                                                deadlock.

The point is about having spinlock_irqsave only _virtually_ masking the interrupts by preventing their associated Linux handler from being called, but despite this, Adeos still actually acquires and acknowledges the incoming hw events before logging them, even if their associated action happen to be postponed until spinlock_irq_restore() is called.

To solve this, all spinlocks potentially touched by the ipipe's primary IRQ handler and/or the code it calls indirectly, _must_ be operated using the _hw() call variant all over the kernel, so that no hw IRQ can be taken while those spinlocks are held by Linux. Usually, only the spinlock(s) protecting the interrupt descriptors or the PIC hardware are concerned.

[   42.660637]  [c000f388] __ipipe_ack_irq+0x88/0x130
[   42.723657]  [c000efe4] __ipipe_handle_irq+0x140/0x268
[   42.791259]  [c000f144] __ipipe_grab_irq+0x38/0xa4
[   42.854279]  [c0005058] __ipipe_ret_from_except+0x0/0xc
[   42.923029]  [00000000] 0x0
[   42.959695]  [c0038348] __do_IRQ+0x134/0x164
[   43.015839]  [c000ed04] __ipipe_do_IRQ+0x2c/0x44
[   43.076567]  [c000eb08] __ipipe_sync_stage+0x1ec/0x228
[   43.144170]  [c0039420] ipipe_suspend_domain+0x7c/0xc4
[   43.211774]  [c000f0b0] __ipipe_handle_irq+0x20c/0x268
[   43.279377]  [c000f144] __ipipe_grab_irq+0x38/0xa4
[   43.342396]  [c0005058] __ipipe_ret_from_except+0x0/0xc
[   43.411145]  [c0006524] default_idle+0x10/0x60


Any ideas of where to look?

Regards

Anders Blomdell



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--

Philippe.

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