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Post/Wait FAQ
What is Post/Wait?
How do I configure my kernel to use Post/Wait?
How do I use the library?
What is Post/Wait?
Post/Wait is an efficient, fast, lightweight sleep/wakeup/timer mechanism used between a cooperating group of processes. A "Wait" call generally causes the process making the call to sleep until 1) the timer expires, 2) the process is "Posted" to by another process in the cooperating group, or 3) the call is interrupted. Thus, a "Wait" can be used either to force a process to sleep for a certain time interval, or to sleep until another process tells it to wake up (or both, whichever happens first). A "Post" call is used to wake up a process sleeping due to a "Wait" call. If the target process is not yet Waiting, the post will be logged, and the process will return immediately the next time it calls "Wait". Note that Posts do not accumulate. Please see the
postwait(3)
man page for more details.
How do I configure my kernel to use Post/Wait?
There are two configuration options for Post/Wait: CONFIG_PW, and CONFIG_PW_VMAX. CONFIG_PW is used to turn on Post/Wait functionality. CONFIG_PW_VMAX is an integral value indicating the maximum number of processes that can be posted to by one library call. These configuration options are found under the "General Setup" menu.
How do I use the library?
In order to use Post/Wait, the user level program must be linked with libdba.so. This library is created by the library patch in the
download
section. The README file, also found in the
download
section, contains specific instructions on how to create this library and link with it.