Re: [patch V2 30/38] posix-cpu-timers: Respect INFINITY for hard RTTIME limit

[Frederic Weisbecker]

On Wed, Aug 21, 2019 at 09:09:17PM +0200, Thomas Gleixner wrote:
> The RTIME limit expiry code does not check the hard RTTIME limit for
> INFINITY, i.e. being disabled.  Add it.
> 
> While this could be considered an ABI breakage if something would depend on
> this behaviour. Though it's highly unlikely to have an effect because
> RLIM_INFINITY is at minimum INT_MAX and the RTTIME limit is in seconds, so
> the timer would fire after ~68 years.
> 
> Adding this obvious correct limit check also allows further consolidation
> of that code and is a prerequisite for cleaning up the 0 based checks and
> the rlimit setter code.
> 
> Signed-off-by: Thomas Gleixner 

Reviewed-by: Frederic Weisbecker 

[patch V2 30/38] posix-cpu-timers: Respect INFINITY for hard RTTIME limit

[Thomas Gleixner]

The RTIME limit expiry code does not check the hard RTTIME limit for
INFINITY, i.e. being disabled.  Add it.

While this could be considered an ABI breakage if something would depend on
this behaviour. Though it's highly unlikely to have an effect because
RLIM_INFINITY is at minimum INT_MAX and the RTTIME limit is in seconds, so
the timer would fire after ~68 years.

Adding this obvious correct limit check also allows further consolidation
of that code and is a prerequisite for cleaning up the 0 based checks and
the rlimit setter code.

Signed-off-by: Thomas Gleixner 
---
V2: Documented the theoretical ABI breakage in the changelong
---
 kernel/time/posix-cpu-timers.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -921,7 +921,7 @@ static void check_process_timers(struct
unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
 
-   if (psecs >= hard) {
+   if (hard != RLIM_INFINITY && psecs >= hard) {
/*
 * At the hard limit, we just die.
 * No need to calculate anything else now.