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Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes
From: |
Svante Signell |
Subject: |
Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads. |
Date: |
Wed, 31 Aug 2016 13:24:34 +0200 |
On Wed, 2016-08-31 at 12:58 +0200, Samuel Thibault wrote:
> Svante Signell, on Wed 31 Aug 2016 12:35:26 +0200, wrote:
> >
> > The attached patch changes this fixing the previous:
> > check_setpriority: can't set priority: Permission denied
> >
> > - prierr = __task_priority (task, NICE_TO_MACH_PRIORITY (prio), 1);
> > + prierr = __task_priority (task, NICE_TO_MACH_PRIORITY (prio), 0);
> Err, but then that makes change_threads false, i.e. the task_priority()
> call will not change the priorities of all threads of the task, which as
> you say is the POSIX behavior:
So a task is equal to a thread, not a process? Leading to change_threads must be
TRUE (to change all threads = process?)
> >
> > According to setpriority(2) and POSIX the nice value should be
> > per-process not per-thread.
> So this "fix" your testcase by making the function not do what it is
> supposed to do...
>
> Re-read your test again: it requests nice -19, i.e. something which is
> reserved to root. No wonder you are getting a permission denied.
Explain please, I get the same output also for running as root:
check_setpriority: can't set priority: Permission denied
> The
> actual bug here is that task_priority seems not to check whether the
> priority is allowed when change_threads is false.
Tracing the call from setpriority() results in KERN_FAILURE from kern/task.c:
if (thread_priority(thread, priority, FALSE) != KERN_SUCCESS)
ret = KERN_FAILURE;
which falls back to the implementation of thread_priority() in kern/thread.c
- RFC: [PATCH] Enable olddelta to be NULL in adjtime(3), Svante Signell, 2016/08/30
- RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Svante Signell, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Samuel Thibault, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads.,
Svante Signell <=
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Samuel Thibault, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Svante Signell, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Samuel Thibault, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Svante Signell, 2016/08/31
- Re: RFC: [PATCH] Fix setpriority calling __task_priority() for processes instead of threads., Samuel Thibault, 2016/08/31
Re: RFC: [PATCH] Enable olddelta to be NULL in adjtime(3), Samuel Thibault, 2016/08/30