Date: Wed, 31 Jan 2001 19:02:20 -0500 From: "Matthew Emmerton" <matt@gsicomp.on.ca> To: "John Baldwin" <jhb@FreeBSD.org> Cc: <freebsd-hackers@FreeBSD.org> Subject: Re: Atomic bit operations Message-ID: <00df01c08be2$3ff1e0e0$1200a8c0@gsicomp.on.ca> References: <XFMail.010131151628.jhb@FreeBSD.org>
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> On 31-Jan-01 Matthew Emmerton wrote: > > Hi all, > > > > I've taken a look around for an implementation of atomic bit operations in > > FreeBSD (similar to Linux' asm/bitopt.h, which include clear_bit() and > > test_and_set_bit()) but haven't found any. The only thing I've found are > > the atomic clear/set/add/sub routines in machine/atomic.h. > > > > Do we have an implementation of atomic bit operations, and if we don't, > > would we like some? > > Erm, atomic_set() sets's bits, and atomic_clear() clear's bits. Anything else > you might need can be done with atomic_cmpset() anyways. Where are these functions implemented? /usr/include/machine/atomic.h just has atomic_set_XXX and clear_XXX primitives, which work on char/short/longs, but not individual bits. I presume that I could wrap the char operations with something that takes 0x01 and bit-shifts it appropriately so that atomic_set/clear could be used. However, certain other primitives are missing, such as an atomic test-and-set operation. Under the current scheme this would have to be done by two independent operations, which is not useful when atomicitiy is required. -- Matt Emmerton To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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