Date: Sat, 21 Jun 2003 19:18:31 -0700 (PDT) From: Ian Dowse <iedowse@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sbin/dmesg dmesg.c src/sys/sys msgbuf.h src/sys/conf files src/sys/kern subr_log.c subr_msgbuf.c subr_prf.c Message-ID: <200306220218.h5M2IVUt087606@repoman.freebsd.org>
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iedowse 2003/06/21 19:18:31 PDT
FreeBSD src repository
Modified files:
sbin/dmesg dmesg.c
sys/sys msgbuf.h
sys/conf files
sys/kern subr_log.c subr_prf.c
Added files:
sys/kern subr_msgbuf.c
Log:
Replace the code for reading and writing the kernel message buffer
with a new implementation that has a mostly reentrant "addchar"
routine, supports multiple message buffers in the kernel, and hides
the implementation details from callers.
The new code uses a kind of sequence number to represend the current
read and write positions in the buffer. This approach (suggested
mainly by bde) permits the read and write pointers to be maintained
separately, which reduces the number of atomic operations that are
required. The "mostly reentrant" above refers to the way that while
it is now always safe to have any number of concurrent writers,
readers could see the message buffer after a writer has advanced
the pointers but before it has witten the new character.
Discussed on: freebsd-arch
Revision Changes Path
1.20 +1 -3 src/sbin/dmesg/dmesg.c
1.796 +1 -0 src/sys/conf/files
1.58 +7 -18 src/sys/kern/subr_log.c
1.1 +239 -0 src/sys/kern/subr_msgbuf.c (new)
1.103 +26 -94 src/sys/kern/subr_prf.c
1.21 +22 -4 src/sys/sys/msgbuf.h
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