pfind() in ithread handler

[pluknet]

On 28/02/2008, Yuri Pankov <yuri.pankov at gmail.com> wrote:
> Hi,
>
>  I'm trying to understand the cause of following panic.
>
>  panic: Trying sleep, but thread marked as sleeping prohibited
>  cpuid = 0
>  KDB: stack backtrace:
>  db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
>  panic() at panic+0x17d
>  sleepq_add() at sleepq_add+0x2e1
>  _sx_slock_hard() at _sx_slock_hard+0x15d
>  _sx_slock() at _sx_slock+0xc1
>  pfind() at pfind+0x24
>  saa_intr() at saa_intr+0x313
>  ithread_loop() at ithread_loop+0xda
>  fork_exit() at fork_exit+0x12a
>  fork_trampoline() at fork_trampoline+0xe
>  --- trap 0, rip = 0, rsp = 0xffffffffac3c0d30, rbp = 0 ---
>
>  Can someone enlighten me on what is causing the panic and is it ok to
>  use pfind() in interrupt handler (I have very limited understanding of
>  kernel internals)?
>
>  Code in question (taken from saa driver
>  http://freebsd.ricin.com/ports/distfiles/kbtv-1.92.tbz) can be found at
>  http://www.pastebin.ca/921830
>
>
>  TIA,
>  Yuri

You cannot sleep in high priority ithread handler, pfind() uses
sleepable sx(9) lock.
In your case it fail to acquire a shared lock and trying to sleep.
Probably you should call pfind() elsewhere.

wbr,
pluknet