Date: Fri, 27 Feb 2015 09:14:10 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Harrison Grundy <harrison.grundy@astrodoggroup.com> Subject: Re: Minor ULE changes and optimizations Message-ID: <2311645.BNIPBaFv2E@ralph.baldwin.cx> In-Reply-To: <54EF2C54.7030207@astrodoggroup.com> References: <54EF2C54.7030207@astrodoggroup.com>
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On Thursday, February 26, 2015 06:23:16 AM Harrison Grundy wrote: > https://reviews.freebsd.org/D1969 > This allows a non-migratable thread to pin itself to a CPU if it is > already running on that CPU. > > I've been running these patches for the past week or so without issue. > Any additional testing or comments would be greatly appreciated. Can you explain the reason / use case for this? This seems to be allowing an API violation. sched_pin() was designed to be a lower-level API than sched_bind(), so you wouldn't call sched_bind() if you were already pinned. In addition, sched_pin() is sometimes used by code that assumes it won't migrate until sched_unpin() (e.g. temporary mappings inside an sfbuf). If you allow sched_bind() to move a thread that is pinned you will allow someone to unintentionally break those sort of things instead of getting an assertion failure panic. -- John Baldwin
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