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SubjectRe: [PATCH 21/23] y2038: itimer: change implementation to timespec64
On Wed, Nov 13, 2019 at 11:28 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> On Fri, 8 Nov 2019, Arnd Bergmann wrote:
> > @@ -321,12 +321,12 @@ TRACE_EVENT(itimer_state,
> > __entry->which = which;
> > __entry->expires = expires;
> > __entry->value_sec = value->it_value.tv_sec;
> > - __entry->value_usec = value->it_value.tv_usec;
> > + __entry->value_usec = value->it_value.tv_nsec / NSEC_PER_USEC;
> > __entry->interval_sec = value->it_interval.tv_sec;
> > - __entry->interval_usec = value->it_interval.tv_usec;
> > + __entry->interval_usec = value->it_interval.tv_nsec / NSEC_PER_USEC;
>
> Hmm, having a division in a tracepoint is clearly suboptimal.

Ok, moving it to the TP_printk() as Steven suggested.

> > - TP_printk("which=%d expires=%llu it_value=%ld.%ld it_interval=%ld.%ld",
> > + TP_printk("which=%d expires=%llu it_value=%ld.%06ld it_interval=%ld.%06ld",
>
> We print only 6 digits after the . so that would be even correct w/o a
> division. But it probably does not matter much.

This is just a cosmetic fix, it can be a separate patch if you care. The idea
is to print the numbers as normal decimal representation, e.g. 0.001000
for a millisecond instead of the nonstandard 0.1000.

> > @@ -197,19 +207,13 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
> > #define timeval_valid(t) \
> > (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
>
> Hrm, why do we have yet another incarnation of timeval_valid()?

No idea, you have to ask the author of commit 7d99b7d634d8 ("[PATCH]
Validate and
sanitze itimer timeval from userspace") ;-)

> Can we please have only one (the inline version)?

I'm removing the inline version in a later patch along with most of the rest of
include/linux/time32.h.

Having the macro version is convenient for this patch, since I'm using it
on two different structures (itimerval/__kernel_old_timeval and
old_itimerval32/old_timeval32), neither of which is the type used in the
inline function.

I could use two local inline functions instead of the macro, or just open
code both call sites if you prefer that.

Arnd

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