On Tue, Jul 18, 2006 at 06:20:20AM -0400, Chuck Ebbert wrote:
> AFAIC the /proc method of controlling seccomp is so ugly it should
> just go, but what about backwards compatibility?
Given that so far CPUShare seems the only user there should be no
problem, I already uploaded a new CPUShare package that handles both
the old and new interfaces transparently, no matter what kernel runs
under it.
> I have a couple of questions:
>
>
> +void disable_TSC(void)
> +{
> + if (!test_and_set_thread_flag(TIF_NOTSC))
> + /*
> + * Must flip the CPU state synchronously with
> + * TIF_NOTSC in the current running context.
> + */
> + hard_disable_TSC();
> +}
>
> This gets called from sys_prctl(). Do you need to worry about preemption
> between the test_and_set and TSC disable?
I tend to completely forget about preempt.
> Maybe these should be inline? They're really small and that way you
> don't need #ifdef around the code for them.
I wanted to reduce the bytecode overhead to the minimum when seccomp
is set to y, for that I tried to avoided inlines.
> For x86_64 you need this:
>
> ftp://ftp.firstfloor.org/pub/ak/x86_64/quilt-current/patches/tif-flags-for-debug-regs-and-io-bitmap-in-ctxsw
>
> But I don't think Andi plans on pushing it for 2.6.18.
Thanks for the pointer.
For now the patch I posted already works on x86-64 and on all other
archs (x86_64 misses the notsc feature for now, but that's not a
problem, the patch is self contained and we can take care of the notsc
for x86-64 later on).
This is the incremental patch to address the preempt=y kernel builds.
diff -r 373f0be00c40 arch/i386/kernel/process.c
--- a/arch/i386/kernel/process.c Sun Jul 16 15:51:54 2006 +0200
+++ b/arch/i386/kernel/process.c Tue Jul 18 14:59:23 2006 +0200
@@ -542,12 +542,14 @@ void hard_disable_TSC(void)
}
void disable_TSC(void)
{
+ preempt_disable();
if (!test_and_set_thread_flag(TIF_NOTSC))
/*
* Must flip the CPU state synchronously with
* TIF_NOTSC in the current running context.
*/
hard_disable_TSC();
+ preempt_enable();
}
void hard_enable_TSC(void)
{
-
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