• Jayachandran C's avatar
    MIPS: Synchronize MIPS count one CPU at a time · cf9bfe55
    Jayachandran C authored
    The current implementation of synchronise_count_{master,slave} blocks
    slave CPUs in early boot until all of them come up. This no longer
    works because blocking a CPU with interrupts off after notifying the
    CPU to be online causes problems with the current kernel.
    
    Specifically, after the workqueue changes
    (commit a08489c5 "Pull workqueue changes from Tejun Heo")
    the CPU_ONLINE notification callback workqueue_cpu_up_callback()
    will hang on wait_for_completion(&idle_rebind.done), if the slave
    CPUs are blocked for synchronize_count_slave().
    
    The changes are to update synchronize_count_{master,slave}() to handle
    one CPU at a time and to call synchronise_count_master() in __cpu_up()
    so that the CPU_ONLINE notification goes out only after the COP0 COUNT
    register is synchronized.
    
    [ralf@linux-mips.org: This matter only to those few platforms which are
    using the cp0 counter as their clocksource which are XLP, XLR and MIPS'
    CMP solution.]
    Signed-off-by: default avatarJayachandran C <jchandra@broadcom.com>
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/4216/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    cf9bfe55
sync-r4k.c 3.7 KB