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Date:      Wed, 29 Nov 2017 17:55:19 -0800
From:      Cy Schubert <Cy.Schubert@komquats.com>
To:        Hans Petter Selasky <hselasky@FreeBSD.org>
Cc:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r326376 - head/sys/kern
Message-ID:  <201711300156.vAU1tJfe070900@slippy.cwsent.com>
In-Reply-To: Message from Hans Petter Selasky <hselasky@FreeBSD.org> of "Wed, 29 Nov 2017 23:28:40 %2B0000." <201711292328.vATNSeOM046518@repo.freebsd.org>

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In message <201711292328.vATNSeOM046518@repo.freebsd.org>, Hans Petter 
Selasky
writes:
> Author: hselasky
> Date: Wed Nov 29 23:28:40 2017
> New Revision: 326376
> URL: https://svnweb.freebsd.org/changeset/base/326376
>
> Log:
>   The sched_add() function is not only used when the thread is initially
>   started, but also by the turnstiles to mark a thread as runnable for
>   all locks, for instance sleepqueues do:
>   setrunnable()->sched_wakeup()->sched_add()
>   
>   In r326218 code was added to allow booting from non-zero CPU numbers
>   by setting the ts_cpu field inside the ULE scheduler's sched_add()
>   function. This had an undesired side-effect that prior sched_pin() and
>   sched_bind() calls got disregarded. This patch fixes the
>   initialization of the ts_cpu field for the ULE scheduler to only
>   happen once when the initial thread is constructed during system
>   init. Forking will then later on ensure that a valid ts_cpu value gets
>   copied to all children.
>   
>   Reviewed by:	jhb, kib
>   Discussed with:	nwhitehorn
>   MFC after:	1 month
>   Differential revision:	https://reviews.freebsd.org/D13298
>   Sponsored by:	Mellanox Technologies
>
> Modified:
>   head/sys/kern/sched_ule.c
>
> Modified: head/sys/kern/sched_ule.c
> =============================================================================
> =
> --- head/sys/kern/sched_ule.c	Wed Nov 29 21:16:14 2017	(r326375)
> +++ head/sys/kern/sched_ule.c	Wed Nov 29 23:28:40 2017	(r326376)
> @@ -1405,7 +1405,6 @@ sched_setup(void *dummy)
>  
>  	/* Add thread0's load since it's running. */
>  	TDQ_LOCK(tdq);
> -	td_get_sched(&thread0)->ts_cpu = curcpu; /* Something valid to start */
>  	thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
>  	tdq_load_add(tdq, &thread0);
>  	tdq->tdq_lowpri = thread0.td_priority;
> @@ -1642,6 +1641,7 @@ schedinit(void)
>  	ts0->ts_ltick = ticks;
>  	ts0->ts_ftick = ticks;
>  	ts0->ts_slice = 0;
> +	ts0->ts_cpu = curcpu;	/* set valid CPU number */
>  }
>  
>  /*
> @@ -2453,7 +2453,6 @@ sched_add(struct thread *td, int flags)
>  	 * Pick the destination cpu and if it isn't ours transfer to the
>  	 * target cpu.
>  	 */
> -	td_get_sched(td)->ts_cpu = curcpu; /* Pick something valid to start */
>  	cpu = sched_pickcpu(td, flags);
>  	tdq = sched_setcpu(td, cpu, flags);
>  	tdq_add(tdq, td, flags);
>

Thank you.


-- 
Cheers,
Cy Schubert <Cy.Schubert@cschubert.com>
FreeBSD UNIX:  <cy@FreeBSD.org>   Web:  http://www.FreeBSD.org

	The need of the many outweighs the greed of the few.





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