Messages in this thread | | | Date | Tue, 12 May 2009 00:40:01 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH -rc] [BUGFIX] x86: fix kernel_trap_sp() |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Mon, 11 May 2009, Masami Hiramatsu wrote: > > > > Use ®s->sp instead of regs for getting the top of stack in kernel mode. > > (on x86-64, regs->sp always points the top of stack) > > Ack. > > That said, we have only _one_ use of this "kernel_trap_sp()" in > the whole kernel, and that use is actually fairly odd too, in that > it does it _before_ checking that it's in kernel mode. > > Admittedly it will then only _use_ the value after it has checked > that things are in kernel mode, but it all boils down to "ok, > that's pretty odd". > > So how about fixing that, and also fixing the naming of the > function. Call it "kernel_stack_pointer()" to match its more > widely used sibling function "user_stack_pointer()". > > IOW, something like this?
yeah, this is cleaner and probably a tad faster. I've applied it to x86/urgent with your acked-by - or would you like to apply this straight away?
The use of the backtracing feature on the oprofile side is not very common (and the bug is ancient) so i wanted to wait a few days with this.
One small detail:
> + return (unsigned long)(®s->sp);
the original commit had:
> + return (unsigned long)®s->sp;
and this latter is correct as well due to operator priorities. No strong preference from my side so i took your version as-is. I kept Masami as the author and a comment for your changes.
( Not sure how to express this in a changelog properly - i didnt want two commits but it was authored by two people in essence. So i went for the version that will show up in the commit notification email in a few minutes - also attached below. )
Ingo
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