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Date: Wed, 19 May 2010 15:36:06 +0100 From: David Howells <dhowells@...hat.com> To: Michel Lespinasse <walken@...gle.com> Cc: dhowells@...hat.com, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Mike Waychison <mikew@...gle.com>, Suleiman Souhlal <suleiman@...gle.com>, Ying Han <yinghan@...gle.com> Subject: Re: [PATCH 09/10] x86 rwsem: down_read_critical implementation Michel Lespinasse <walken@...gle.com> wrote: > The basic properties that have been true so far still hold: > - RWSEM_ACTIVE_READ_BIAS & RWSEM_ACTIVE_MASK == 1 > - RWSEM_ACTIVE_WRITE_BIAS & RWSEM_ACTIVE_MASK == 1 > - RWSEM_WAITING_BIAS & RWSEM_ACTIVE_MASK == 0 > - RWSEM_ACTIVE_WRITE_BIAS < 0 and RWSEM_WAITING_BIAS < 0 > > A new property is introduced: RWSEM_ACTIVE_WRITE_BIAS is set to be > 'more negative' than RWSEM_WAITING_BIAS. This way, even the first writer > will set the rwsem count to be < RWSEM_WAITING_BIAS and down_read_critical() > can make use of this to determine if there are any active writers. > > Signed-off-by: Michel Lespinasse <walken@...gle.com> Acked-by: David Howells <dhowells@...hat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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