Re: Current port status

[Frank Wille <frank%phoenix.owl.de@localhost>]

matthew green wrote:

> 0xa94a3940: at vpanic+0x21c
> 0xa94a3970: at panic+0x4c
> 0xa94a39b0: at lockdebug_abort1+0xdc
> 0xa94a39d0: at mutex_abort+0x50
> 0xa94a39e0: at mutex_enter+0x26c                          [5]
> 0xa94a3a20: at pool_get+0x7c                              [4]
> 0xa94a3a60: at pool_cache_get_slow+0x214
> 0xa94a3a90: at pool_cache_get_paddr+0x290
> 0xa94a3ae0: at m_get+0x3c
> 0xa94a3af0: at m_gethdr+0xc
> 0xa94a3b00: at vr_rxeof+0x3c8
> 0xa94a3b70: at vr_intr+0x314
> 0xa94a3bb0: at intr_deliver+0x7c
> 0xa94a3bf0: at pic_do_pending_int+0x12c
> 0xa94a3c30: at splx+0x38                                  [3]
> 0xa94a3c40: at lockdebug_unlocked+0x190                   [2]
> 0xa94a3c70: at mutex_exit+0x194                           [1]
> 0xa94a3c90: at pool_get+0x1f8
> 0xa94a3cd0: at pool_cache_get_slow+0x214
> [...]
> splx() call to return to the previous IPL.  at this point in [3] we
> check for other interrupts at higher levels, and we end up having a PCI
> intr on the vr. eventually this goes down to [4], which is operating on
> the same pool as the mutex in [1] belongs to but hasn't actually been
> completely released yet,

This is something I don't understand. Obviously mutex_exit() had been called
in [1] for this pool, so why didn't it have been "completely released" when
entering again in [5]?

I don't know very much about the internals of kernel mutexes, but when
mutex_exit() would really call splx() before having released everything
this sounds like a bug in mutex_exit(), which is hard to believe as it
works in most other environments.

-- 
Frank Wille