NetBSD Problem Report #40505

From www@NetBSD.org  Wed Jan 28 15:07:19 2009
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Date: Wed, 28 Jan 2009 15:07:19 +0000 (UTC)
From: pooka@iki.fi
Reply-To: pooka@iki.fi
To: gnats-bugs@NetBSD.org
Subject: delay(9) is a MD non-interface
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>Number:         40505
>Category:       kern
>Synopsis:       delay(9) is a MD non-interface
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 28 15:10:00 +0000 2009
>Last-Modified:  Sat Jul 19 10:05:01 +0000 2014
>Originator:     Antti Kantee
>Release:        
>Organization:
interfaces r us
>Environment:
>Description:
delay and DELAY use various cpp tricks from port to port.  There
should be only an MI interface definition.
>How-To-Repeat:
little reading
>Fix:
lot of writing

>Audit-Trail:
From: Masao Uebayashi <uebayasi@gmail.com>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: kern/40505: delay(9) is a MD non-interface
Date: Sat, 19 Jul 2014 09:58:26 +0900

 For sys/kern/subr_prf.c:vpanic(), whose DELAY() is "I have nothing to
 do", it can be replaced with MI function cpu_idle().  Question is, how
 to implement it in rump.

From: Antti Kantee <pooka@iki.fi>
To: gnats-bugs@NetBSD.org, kern-bug-people@netbsd.org, 
 gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
Cc: 
Subject: Re: kern/40505: delay(9) is a MD non-interface
Date: Sat, 19 Jul 2014 10:03:57 +0000

 On 19/07/14 01:00, Masao Uebayashi wrote:
 >   For sys/kern/subr_prf.c:vpanic(), whose DELAY() is "I have nothing to
 >   do", it can be replaced with MI function cpu_idle().  Question is, how
 >   to implement it in rump.

 cpu_idle() is not a MI function interface, from cpu.h:
 #ifndef cpu_idle
 void cpu_idle(void);
 #endif

 For that particular DELAY(), it might as well be "continue".

 But to answer your question anyway: you can't meaningfully, rump kernels 
 do not schedule threads onto cores (they run on threads which schedule 
 cores), so "core is idle" does not make sense.

 If you really have a strong use case for not spinning before reboot in 
 case >1 cores panic, from the rump kernel perspective it is best to 
 define a true interface, e.g. cpu_panicwait(), and call cpu_idle() in 
 the kern_cpu.c implementation and sleep in a rump kernel.

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