Messages in this thread | | | Subject | Re: [PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread. | From | Arjan van de Ven <> | Date | Fri, 5 Feb 2016 18:15:47 -0800 |
| |
On 2/5/2016 4:51 PM, John Stultz wrote: > On Fri, Feb 5, 2016 at 2:35 PM, John Stultz <john.stultz@linaro.org> wrote: >> On Fri, Feb 5, 2016 at 12:50 PM, Andrew Morton >> <akpm@linux-foundation.org> wrote: >>> On Fri, 5 Feb 2016 12:44:04 -0800 Kees Cook <keescook@chromium.org> wrote: >>>> Could this be exposed as a writable /proc entry instead? Like the oom_* stuff? >>> >>> /proc/<pid>/timer_slack_ns, guarded by ptrace_may_access(), documented >>> under Documentation/? Yup, that would work. It's there for all >>> architectures from day one and there is precedent. It's not as nice, >>> but /proc nasties will always be with us. >> >> Ok. I'll start working on that. > > Arjan/Thomas: One curious thing I noticed here while writing some > documentation. The timer_slack_ns value in the task struct is a > unsigned long. > > So this means PR_SET_TIMERSLACK limits the maximum slack on 32 bit > machines to ~4 seconds. Where on 64bit machines it can be quite a bit > longer (unreasonably long, really :).
originally when we created timerslack, 4 seconds was an eternity and good enough for everyone by a mile... (assumption was practical upper limit being in the 15 msec range) and most of the RT guys would only tolerate a little bit of it
is there any real/practial use of going longer than 4 seconds? if there is then yeah fixing it makes sense. if it's just theoretical... shrug... 32 bit systems have a bunch of other limits/differences a well.
| |