Regression with orderly_poweroff()

[Benjamin Herrenschmidt]

Hi Linus !

A couple of weeks ago, David sent an email that went unanswered about a
regression concerning orderly_poweroff(). I think the original patch
causing it should be reverted, here's the actual email with the
explanation:

<<<
Subject: orderly_poweroff() is no longer safe in atomic context

Commit 6c0c0d4d1080840eabb3d055d2fd81911111c5fd "poweroff: fix bug in
orderly_poweroff()" apparently fixes one bug in orderly_poweroff(),
but introduces another.  The comments on orderly_poweroff() claim it
can be called from any context - and indeed we call it from interrupt
context in arch/powerpc/platforms/pseries/ras.c for example.  But
since that commit this is no longer safe, since
call_usermodehelper_fns() is not safe in interrupt context without the
UMH_NO_WAIT option.

I'm having trouble understanding the commit message to see what the
original bug being fixed was.  Specifically I can't make sense of:

  |  The bug here is, step 1 is always successful with param
  |  UMH_NO_WAIT, which obey the design goal of orderly_poweroff.

And without understanding the original bug, I'm not sure what the
correct fix is.
>>>

Cheers,
Ben.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/