On Tue, Jan 09, 2007 at 07:19:29PM +0300, Alexei Sheplyakov wrote:
> chpst -n seems to always sets the nice value to 19 on x86_64, no
> matter what argument has been given:
>
> $ chpst -n 5 ps -l
> F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
> 0 S 1000 11267 10824 0 75 0 - 2634 - pts/7 00:00:00 bash
> 0 R 1000 11742 11267 0 97 19 - 1892 - pts/7 00:00:00 ps
>
> On the other hand, chpst works just fine on x86:
>
> [on the x86 box]
> $ chpst -n 5 ps -l
> F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
> 0 S 1000 14282 23386 4 75 0 - 2928 - pts/3 00:00:00 bash
> 0 R 1000 5586 14282 0 82 5 - 1827 - pts/3 00:00:00 ps
>
>
> [on the x86_64 box]
> $ strace -f chpst -n 5 /bin/true 2>&1 | head -n 5
> execve("/usr/bin/chpst", ["chpst", "-n", "5", "/bin/true"], [/* 68 vars */])
> = 0
> getpriority(PRIO_PROCESS, 0) = 20
> setpriority(PRIO_PROCESS, 0, 25) = 0
> getpriority(PRIO_PROCESS, 0) = 1
> execve("/bin/true", ["/bin/true"], [/* 68 vars */]) = 0
>
> On Linux, "getpriority()" will not return the normal nice-value, but
> a negated value that has been offset by 20 (ie it returns 40..1 instead
> of -20..19) to avoid negative return values.
>
> On the other hand, "setpriority" accepts _regular_ nice value in the
> range -20..19. chpst seems to ignore this difference and sets wrong
> nice value as a result.
Thanks for the report, Alexei.
> x86 is not affected since chpst uses "nice" system call here:
The bug actually is in the dietlibc; not in runit's chpst, which uses
nice() on all archs.
Regards, Gerrit.
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