Date: Tue, 15 May 2001 15:14:00 +0900 From: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> To: jhb@FreeBSD.org Cc: tanimura@r.dl.itc.u-tokyo.ac.jp, current@FreeBSD.org Subject: atomic operation of flags (was: RE: select(2) converted to use a condition variable, and optimis) Message-ID: <200105150614.f4F6E0P53295@rina.r.dl.itc.u-tokyo.ac.jp> In-Reply-To: In your message of "Mon, 07 May 2001 12:37:22 -0700 (PDT)" <XFMail.010507123722.jhb@FreeBSD.org> References: <200105060731.f467V4g13184@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> <XFMail.010507123722.jhb@FreeBSD.org>
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On Mon, 07 May 2001 12:37:22 -0700 (PDT), John Baldwin <jhb@FreeBSD.org> said: John> You need the lock when clearing the bit in p_flag. That is why the proc locks John> are there, so all those proc locks need to stay. When you clear a bit, you are John> writing all the bits, so you need to ensure that you can atomically John> read/modify/write all the bits in p_flag, hence the need for the proc lock. As we now have a set of atomic operation functions in machine/atomic.h, why do we not use them to read, modify and write p_flag atomically? Is that more expensive than protecting by PROC_LOCK and PROC_UNLOCK? -- Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> <tanimura@FreeBSD.org> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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