svn commit: r358483 - head/sys/compat/linux

[Tijl Coosemans]

On Thu, 5 Mar 2020 16:15:10 +0300 Yuri Pankov <ypankov at fastmail.com>
wrote:
> Tijl Coosemans wrote:
>> Author: tijl
>> Date: Sun Mar  1 13:12:04 2020
>> New Revision: 358483
>> URL: https://svnweb.freebsd.org/changeset/base/358483
>> 
>> Log:
>>    linuxulator: Map scheduler priorities to Linux priorities.
>>    
>>    On Linux the valid range of priorities for the SCHED_FIFO and SCHED_RR
>>    scheduling policies is [1,99].  For SCHED_OTHER the single valid priority is
>>    0.  On FreeBSD it is [0,31] for all policies.  Programs are supposed to
>>    query the valid range using sched_get_priority_(min|max), but of course some
>>    programs assume the Linux values are valid.
>>    
>>    This commit adds a tunable compat.linux.map_sched_prio.  When enabled
>>    sched_get_priority_(min|max) return the Linux values and sched_setscheduler
>>    and sched_(get|set)param translate between FreeBSD and Linux values.
>>    
>>    Because there are more Linux levels than FreeBSD levels, multiple Linux
>>    levels map to a single FreeBSD level, which means pre-emption might not
>>    happen as it does on Linux, so the tunable allows to disable this behaviour.
>>    It is enabled by default because I think it is unlikely that anyone runs
>>    real-time software under Linux emulation on FreeBSD that critically relies
>>    on correct pre-emption.
>>    
>>    This fixes FMOD, a commercial sound library used by several games.
>>    
>>    PR:		240043
>>    Tested by:	Alex S <iwtcex at gmail.com>
>>    Reviewed by:	dchagin
>>    MFC after:	2 weeks
>>    Differential Revision:	https://reviews.freebsd.org/D23790
>> 
>> Modified:
>>    head/sys/compat/linux/linux_misc.c
>>    head/sys/compat/linux/linux_misc.h
>> 
>> Modified: head/sys/compat/linux/linux_misc.c
>> ==============================================================================
>> --- head/sys/compat/linux/linux_misc.c	Sun Mar  1 12:34:27 2020	(r358482)
>> +++ head/sys/compat/linux/linux_misc.c	Sun Mar  1 13:12:04 2020	(r358483)
>> @@ -144,6 +144,11 @@ struct l_pselect6arg {
>>   	l_size_t	ss_len;
>>   };
>>   
>> +static bool map_sched_prio = true;
>> +SYSCTL_BOOL(_compat_linux, OID_AUTO, map_sched_prio, CTLFLAG_RDTUN,
>> +    &map_sched_prio, 0, "Map scheduler priorities to Linux priorities "
>> +    "(not POSIX compliant)");  
> 
> I'm seeing the following in the log:
> 
> sysctl_warn_reuse: can't re-use a leaf (compat.linux.map_sched_prio)!
> 
> Should this be done for both linux and linux32 (when one exists) or made 
> to install one time only?

Ah, thanks for the report, I've moved it to linux_common in r358673.