K 10
svn:author
V 7
davidxu
K 8
svn:date
V 27
2010-11-02T06:47:18.115188Z
K 7
svn:log
V 606
Implement userland sleep queue. The queue is used to eliminate extra
context switches and system calls in condition variable use. The
problem is pthread_cond_broadcast can cause thread scheduler's thundering
hurd, and because a thread calls pthread_cond_signal or pthread_cond_broadcast
with mutex locked, resumed thread tries to lock the mutex and is block
again, this is extra context switch. The change tries to move sleeping
threads from condition variable's wait queue to mutex wait queue, only
when the mutex is unlocked, a sleeping thread is woken up, in ideal case,
only one system call is needed.

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