Messages in this thread | | | Date | Thu, 24 Jan 2008 03:01:53 +0800 | From | "Wang Nan" <> | Subject | Can any one tell me why cond_resched in do_select? |
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Hi, everyone. I have a question regarding to select system call's code. In do_select() function, after check each fd in the set, do_select() call cond_resched(). That line, according to my view, is to reduce the system freeze time when do the busy querying. But before the call, when entering into the big loop, do_select call set_current_state(TASK_INTERRUPTIBLE). Then, if the reschedule really taken up, the current process will not return unless it catch a signal, or one of already registered fd send an event. I've tried in UML. If I replace the cond_resched() into schedule(), when sys_select() called, the process halt just like I've said. I don't think there is a bug because this code exist so long time and no really bad thing happened. I just want to know that, since no schedule() allowed here, can we delete the useless line? Thank you.
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