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The kernel uses two ways to write data on a pipe:

Browse Source 
o  buffered write, for chunks smaller than PIPE_MINDIRECT bytes
    o  direct write, for everything else

A call to writev(2) may receive struct iov of various size and the
kernel may have to switch from one solution to the other. Before doing
this, it must wake reader processes and any select/poll/kqueue up.

This commit fixes a bug where select/poll/kqueue are not triggered
when switching from buffered write to direct write. It adds calls to
pipeselwakeup().

I give more details on freebsd-arch@:
http://lists.freebsd.org/pipermail/freebsd-arch/2007-September/006790.html

This should fix issues with Erlang (lang/erlang) and kqueue.

Reported by:	Rickard Green (Erlang)
This commit is contained in:
Jean-Sébastien Pédron 2007-11-19 15:05:20 +00:00
parent f2bd4453a8
commit 4b5b09e744
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=173750
1 changed files with 4 additions and 0 deletions
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4
sys/kern/sys_pipe.c
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@ -880,6 +880,7 @@ pipe_direct_write(wpipe, uio)
wpipe->pipe_state &= ~PIPE_WANTR;
wakeup(wpipe);
}
pipeselwakeup(wpipe);
wpipe->pipe_state |= PIPE_WANTW;
pipeunlock(wpipe);
error = msleep(wpipe, PIPE_MTX(wpipe),
@ -895,6 +896,7 @@ pipe_direct_write(wpipe, uio)
wpipe->pipe_state &= ~PIPE_WANTR;
wakeup(wpipe);
}
pipeselwakeup(wpipe);
wpipe->pipe_state |= PIPE_WANTW;
pipeunlock(wpipe);
error = msleep(wpipe, PIPE_MTX(wpipe),
@ -1080,6 +1082,8 @@ pipe_write(fp, uio, active_cred, flags, td)
wpipe->pipe_state &= ~PIPE_WANTR;
wakeup(wpipe);
}
pipeselwakeup(wpipe);
wpipe->pipe_state |= PIPE_WANTW;
pipeunlock(wpipe);
error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
"pipbww", 0);