Date: Wed, 11 Feb 2009 16:28:49 +0000 (UTC) From: Ed Schouten <ed@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/kern tty.c src/sys/sys tty.h src/usr.sbin/pstat pstat.8 pstat.c Message-ID: <200902111633.n1BGXOMN051369@repoman.freebsd.org>
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ed 2009-02-11 16:28:49 UTC
FreeBSD src repository
Modified files:
sys/kern tty.c
sys/sys tty.h
usr.sbin/pstat pstat.8 pstat.c
Log:
SVN rev 188487 on 2009-02-11 16:28:49Z by ed
Serialize write() calls on TTYs.
Just like the old TTY layer, the current MPSAFE TTY layer does not make
any attempt to serialize calls of write(). Data is copied into the
kernel in 256 (TTY_STACKBUF) byte chunks. If a write() call occurs at
the same time, the data may interleave. This is especially likely when
the TTY starts blocking, because the output queue reaches the high
watermark.
I've implemented this by adding a new flag, TTY_BUSY_OUT, which is used
to mark a TTY as having a thread stuck in write(). Because I don't want
non-blocking processes to be possibly blocked by a sleeping thread, I'm
still allowing it to bypass the protection. According to this message,
the Linux kernel returns EAGAIN in such cases, but I think that's a
little too restrictive:
http://kerneltrap.org/index.php?q=mailarchive/linux-kernel/2007/5/2/85418/thread
PR: kern/118287
Revision Changes Path
1.309 +24 -6 src/sys/kern/tty.c
1.113 +3 -0 src/sys/sys/tty.h
1.54 +5 -0 src/usr.sbin/pstat/pstat.8
1.109 +5 -0 src/usr.sbin/pstat/pstat.c
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