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    SubjectRe: [PATCH] make setpriority POSIX compliant; introduce PRIO_THREAD extension
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    On Mon, 2008-09-01 at 17:08 +0200, Peter Zijlstra wrote:
    > On Mon, 2008-09-01 at 16:42 +0200, Denys Vlasenko wrote:
    > > On Mon, 2008-09-01 at 16:12 +0200, Denys Vlasenko wrote:
    > > > Patch is run tested. I will post test program etc as a reply.
    > >
    > > Looks like Evolution word-wrapped the patch. Let me try again.
    >
    > Patch looks simple enough, although a few comments below.
    > Also, I guess the glibc people (Ulrich added to CC) might have an
    > opinion.
    >
    > > Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
    > > --
    > > vda
    > >
    > >
    > > diff --git a/include/linux/resource.h b/include/linux/resource.h
    > > index aaa423a..f292690 100644
    > > --- a/include/linux/resource.h
    > > +++ b/include/linux/resource.h
    > > @@ -51,6 +51,7 @@ struct rlimit {
    > > #define PRIO_PROCESS 0
    > > #define PRIO_PGRP 1
    > > #define PRIO_USER 2
    > > +#define PRIO_THREAD 3
    > >
    > > /*
    > > * Limit the stack by to some sane default: root can always
    > > diff --git a/kernel/sys.c b/kernel/sys.c
    > > index 038a7bc..d339c1a 100644
    > > --- a/kernel/sys.c
    > > +++ b/kernel/sys.c
    > > @@ -142,9 +142,9 @@ asmlinkage long sys_setpriority(int which, int who, int niceval)
    > > struct task_struct *g, *p;
    > > struct user_struct *user;
    > > int error = -EINVAL;
    > > - struct pid *pgrp;
    > > + struct pid *pgrp, *pid;
    > >
    > > - if (which > PRIO_USER || which < PRIO_PROCESS)
    > > + if (which > PRIO_THREAD || which < PRIO_PROCESS)
    > > goto out;
    > >
    > > /* normalize: avoid signed division (rounding problems) */
    > > @@ -156,7 +156,7 @@ asmlinkage long sys_setpriority(int which, int who, int niceval)
    > >
    > > read_lock(&tasklist_lock);
    > > switch (which) {
    > > - case PRIO_PROCESS:
    > > + case PRIO_THREAD:
    > > if (who)
    > > p = find_task_by_vpid(who);
    > > else
    > > @@ -164,6 +164,19 @@ asmlinkage long sys_setpriority(int which, int who, int niceval)
    > > if (p)
    > > error = set_one_prio(p, niceval, error);
    > > break;
    > > + case PRIO_PROCESS:
    > > + if (who)
    > > + pid = find_vpid(who);
    > > + else {
    > > + pid = task_pid(current);
    > > + who = current->pid;
    > > + }
    > > + do_each_pid_thread(pid, PIDTYPE_PID, p) {
    > > + if (who == p->pid || who == p->tgid) {
    > > + error = set_one_prio(p, niceval, error);
    > > + }
    > > + } while_each_pid_thread(pid, PIDTYPE_PID, p);
    >
    > I worry about destroying the return value here, support one thread
    > fails, but the next succeeds, should we still report failure?

    Hmm. I think we should fail only if they all failed.
    I don't feel strongly either way. Ulrich what do you prefer?

    > > + case PRIO_PROCESS:
    > > + if (who)
    > > + pid = find_vpid(who);
    > > + else {
    > > + pid = task_pid(current);
    > > + who = current->pid;
    > > + }
    > > + do_each_pid_thread(pid, PIDTYPE_PID, p) {
    > > + if (who == p->pid || who == p->tgid) {
    > > + niceval = 20 - task_nice(p);
    > > + if (niceval > retval)
    > > + retval = niceval;
    > > + }
    > > + } while_each_pid_thread(pid, PIDTYPE_PID, p);
    >
    > So we basically return the highest prio amongst the threads?

    Yes. This is analogous to what happens with PRIO_USER etc,
    no surprises here.
    --
    vda




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