From: Geoff Levand <geoffrey.levand@am•sony.com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, David Gibson <david@gibson•dropbear.id.au>
Subject: Re: [PATCH 3/3] zImage: Cleanup and improve zImage entry point
Date: Mon, 19 Feb 2007 13:14:50 -0800 [thread overview]
Message-ID: <45DA134A.2030602@am.sony.com> (raw)
In-Reply-To: <1171918206.18571.66.camel@localhost.localdomain>
Benjamin Herrenschmidt wrote:
> On Mon, 2007-02-19 at 12:37 -0800, Geoff Levand wrote:
>> Benjamin Herrenschmidt wrote:
>> >> This messed me up a bit since I had two stacks in the bss, one for each
>> >> processor thread. By the time this was called on the primary thread the
>> >> secondary thread could already be using its stack. I changed the secondary
>> >> thread to use a small stack in the data section, so this seems OK.
>> >
>> > The secondary thread(s) don't need a stack to loop in secondary hold,
>> > right ? So maybe we could go all the way without using a stack. Do we
>> > need C code at all for them ? We just need to hold them until we make
>> > them branch to the kernel.
>>
>> I thought it would be nice to be able to use printf() in there so you
>> see the following. Its handy for debugging.
>>
>> smp_secondary_hold:307: released cpu (1)
>
> The problem is if your secondary CPUs start using printf etc... that
> means you probably need to get in some locking primitives and make
> various bits of the zImage wrapper SMP safe... pretty scary don't you
> think ? :-)
If you want to make it idiot proof, yes, but I was thinking more that
smp_secondary_hold just prints a final debug message after the primary
is done. It does cause problems if there are more than one secondary.
> I'd rather leave all non-0 CPUs in an asm holding loop. However, you can
> still print some status. One of the ideas is to have them fill up a
> byte-map of present CPUs when they get in the holding loop, then the
> main CPU can "see" them coming in and print something.
I was more interested in seeing that the secondary left smp_secondary_hold,
not that it entered it. I don't really want to add the complexity to make
the primary wait for the secondaries to exit and then print a message.
-Geoff
next prev parent reply other threads:[~2007-02-19 21:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-16 6:24 [0/3] RFC: Cleanups and improvements to the zImage wrapper David Gibson
2007-02-16 6:27 ` [PATCH 3/3] zImage: Cleanup and improve zImage entry point David Gibson
2007-02-18 1:22 ` Geoff Levand
2007-02-18 7:23 ` David Gibson
2007-02-19 0:26 ` Paul Mackerras
2007-02-19 0:48 ` David Gibson
2007-02-19 15:14 ` Geoff Levand
2007-02-19 19:59 ` Benjamin Herrenschmidt
2007-02-19 19:57 ` Benjamin Herrenschmidt
2007-02-19 20:37 ` Geoff Levand
2007-02-19 20:50 ` Benjamin Herrenschmidt
2007-02-19 21:14 ` Geoff Levand [this message]
2007-02-16 6:27 ` [PATCH 2/3] zImage: Cleanup and improve prep_kernel() David Gibson
2007-02-18 1:22 ` Geoff Levand
2007-02-18 7:21 ` David Gibson
2007-02-16 6:27 ` [PATCH 1/3] zImage: Add more flexible gunzip convenience functions David Gibson
2007-02-16 16:47 ` [0/3] RFC: Cleanups and improvements to the zImage wrapper Geoff Levand
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