On Wed, 2015-01-14 at 13:03 -0500, Steven Rostedt wrote:
> On Wed, 14 Jan 2015 09:35:17 +1100
> Michael Ellerman <m...@ellerman.id.au> wrote:
>
> > In commit 5f893b2639b2 "tracing: Move enabling tracepoints to just after
> > rcu_init()", tracing was enabled earlier in boot.
> >
> > This broke tracing of the raw_syscall tracepoints from boot using the
> > trace_event kernel parameter.
> >
> > We can fix it by explicitly setting TIF_SYSCALL_TRACEPOINT for the
> > init_task. That way when pid 1 is cloned from init_task it will inherit
> > TIF_SYSCALL_TRACEPOINT.
>
> I don't like setting the swap task flag for syscall tracing, as nothing
> will unset it.
We could unset it in the unregfunc(), I did that in my original patch but took
it out because I wasn't sure it was necessary.
> > It feels a bit naughty to be whacking init_task like this, but it also
> > seems like the right fix?
>
> No, I tried the following instead.
>
> > Should we also clear it in the unregfunc? I can't see how that would
> > ever be needed in practice?
>
> It just seems hacky to set swapper in the first place.
Actually I thought it was neat, basically everything else comes from init_task
via copy_process().
> Try my patch and let me know if it works for you?
Sure. It works.
I can still see the first syscalls in the trace:
# entries-in-buffer/entries-written: 1021354/1021354 #P:8
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
init-1 [000] .... 3.706370: sys_exit: NR -1 = 0
init-1 [000] .... 3.706394: sys_enter: NR 45 (0, 0,
3fffa2e20000, 3fffcfd4eac2, 80, 3fffa2e61820)
init-1 [000] .... 3.706395: sys_exit: NR 45 =
70367490932736
init-1 [000] .... 3.706409: sys_enter: NR 33
(3fffa2e694d0, 0, 3fffa2e7be20, 0, 1, ffffffffe0000000)
init-1 [000] .... 3.713325: sys_exit: NR 33 = -2
I like my version better, but your call.
cheers
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
