• Nick Piggin's avatar
    [PATCH] sched: disable preempt in idle tasks · 5bfb5d69
    Nick Piggin authored
    
    
    Run idle threads with preempt disabled.
    
    Also corrected a bugs in arm26's cpu_idle (make it actually call schedule()).
    How did it ever work before?
    
    Might fix the CPU hotplugging hang which Nigel Cunningham noted.
    
    We think the bug hits if the idle thread is preempted after checking
    need_resched() and before going to sleep, then the CPU offlined.
    
    After calling stop_machine_run, the CPU eventually returns from preemption and
    into the idle thread and goes to sleep.  The CPU will continue executing
    previous idle and have no chance to call play_dead.
    
    By disabling preemption until we are ready to explicitly schedule, this bug is
    fixed and the idle threads generally become more robust.
    
    From: alexs <ashepard@u.washington.edu>
    
      PPC build fix
    
    From: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>
    
      MIPS build fix
    Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
    Signed-off-by: default avatarYoichi Yuasa <yuasa@hh.iij4u.or.jp>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    5bfb5d69
smp.c 4.2 KB