Re: [PATCH] make setpriority POSIX compliant; introduce PRIO_THREAD extension

Peter Zijlstra
2008-09-01T15:09:18Z

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?

> + break;
> case PRIO_PGRP:
> if (who)
> pgrp = find_vpid(who);
> @@ -206,14 +219,14 @@ asmlinkage long sys_getpriority(int which, int who)
> struct task_struct *g, *p;
> struct user_struct *user;
> long niceval, retval = -ESRCH;
> - struct pid *pgrp;
> + struct pid *pgrp, *pid;
>
> - if (which > PRIO_USER || which < PRIO_PROCESS)
> + if (which > PRIO_THREAD || which < PRIO_PROCESS)
> return -EINVAL;
>
> read_lock(&tasklist_lock);
> switch (which) {
> - case PRIO_PROCESS:
> + case PRIO_THREAD:
> if (who)
> p = find_task_by_vpid(who);
> else
> @@ -224,6 +237,21 @@ asmlinkage long sys_getpriority(int which, int who)
> retval = niceval;
> }
> 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) {
> + 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?

> + break;
> case PRIO_PGRP:
> if (who)
> pgrp = find_vpid(who);
>
>
> --
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