On Sun, Dec 13, 2009 at 08:02:24PM +0000, David Laight wrote: > Log Message: > Another, better, fix for PR/26567. > Only sleep once within each pipe_read/pipe_write call. > If there is no data/space available after we wakeup return ERESTART so > then the 'fd' number is validated again. > A simple broadcast of the cvs is then enough to evict the correct threads > when close() is called from an active thread.
Isn't this going to cause a thundering herd problem if there are a lot of readers competing for the input? The first one will wake up and consume the available data, and then the rest will take a trip all the way to userspace and back. This may or may not be a practical problem for pipes but I'd expect the same approach to suck pretty hard for e.g. accept() on sockets. :( -- David A. Holland dholl...@netbsd.org
