2016-12-07 17:21 GMT+01:00 Vlastimil Babka <vbabka@suse.cz>:

> On 12/07/2016 04:39 PM, Federico Reghenzani wrote:
> > Hello,
> >
> > I'm working on Real-Time applications in Linux. `mlockall()` is a
> > typical syscall used in RT processes in order to avoid page faults.
> > However, the use of this syscall is strongly limited by ulimits, so
> > basically all RT processes that want to call `mlockall()` have to be
> > executed with root privileges.
>
> Is it not possible to change the ulimits with e.g. prlimit?
>
>
Yes, but it requires a synchronization between non-root process and root
process.
Because the root process has to change the limits before the non-root
process executes the mlockall().

Just to provide an example, another syscall used in RT tasks is the
sched_setscheduler() that also suffers
the limitation of ulimits, but it accepts the pid so the scheduling policy
can be enforced by a root process to
any other process.



> > What I would like to have is a syscall that accept a "pid", so a process
> > spawned by root would be able to enforce the memory locking to other
> > non-root processes. The prototypes would be:
> >
> > int mlockall(int flags, pid_t pid);
> > int munlockall(pid_t pid);
> >
> > I checked the source code and it seems to me quite easy to add this
> > syscall variant.
> >
> > I'm writing here to have a feedback before starting to edit the code. Do
> > you think that this is a good approach?
> >
> >
> > Thank you,
> > Federico
> >
> > --
> > *Federico Reghenzani*
> > PhD Candidate
> > Politecnico di Milano
> > Dipartimento di Elettronica, Informazione e Bioingegneria
> >
>
>


-- 
*Federico Reghenzani*
PhD Candidate
Politecnico di Milano
Dipartimento di Elettronica, Informazione e Bioingegneria