• Ming Lei's avatar
    lib/percpu_counter.c: fix __percpu_counter_add() · 74e72f89
    Ming Lei authored
    __percpu_counter_add() may be called in softirq/hardirq handler (such
    as, blk_mq_queue_exit() is typically called in hardirq/softirq handler),
    so we need to call this_cpu_add()(irq safe helper) to update percpu
    counter, otherwise counts may be lost.
    
    This fixes the problem that 'rmmod null_blk' hangs in blk_cleanup_queue()
    because of miscounting of request_queue->mq_usage_counter.
    
    This patch is the v1 of previous one of "lib/percpu_counter.c:
    disable local irq when updating percpu couter", and takes Andrew's
    approach which may be more efficient for ARCHs(x86, s390) that
    have optimized this_cpu_add().
    Signed-off-by: default avatarMing Lei <tom.leiming@gmail.com>
    Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
    Cc: Shaohua Li <shli@fusionio.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Fan Du <fan.du@windriver.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    74e72f89
percpu_counter.c 5.26 KB