From 74e72f894d56eb9d2e1218530c658e7d297e002b Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 14 Jan 2014 17:56:42 -0800 Subject: lib/percpu_counter.c: fix __percpu_counter_add() __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: Ming Lei Cc: Paul Gortmaker Cc: Shaohua Li Cc: Jens Axboe Cc: Fan Du Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/percpu_counter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'lib/percpu_counter.c') diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 7473ee3b4ee..1da85bb1bc0 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -82,10 +82,10 @@ void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); fbc->count += count; + __this_cpu_sub(*fbc->counters, count); raw_spin_unlock_irqrestore(&fbc->lock, flags); - __this_cpu_write(*fbc->counters, 0); } else { - __this_cpu_write(*fbc->counters, count); + this_cpu_add(*fbc->counters, amount); } preempt_enable(); } -- cgit v1.2.3-70-g09d2 From d1969a84dd6a44d375aa82bba7d6c38713a429c3 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Thu, 16 Jan 2014 15:26:48 -0800 Subject: percpu_counter: unbreak __percpu_counter_add() Commit 74e72f894d56 ("lib/percpu_counter.c: fix __percpu_counter_add()") looked very plausible, but its arithmetic was badly wrong: obvious once you see the fix, but maddening to get there from the weird tmpfs ENOSPCs Signed-off-by: Hugh Dickins Cc: Ming Lei Cc: Paul Gortmaker Cc: Shaohua Li Cc: Jens Axboe Cc: Fan Du Cc: Andrew Morton Signed-off-by: Linus Torvalds --- lib/percpu_counter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib/percpu_counter.c') diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 1da85bb1bc0..8280a5dd172 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -82,7 +82,7 @@ void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) unsigned long flags; raw_spin_lock_irqsave(&fbc->lock, flags); fbc->count += count; - __this_cpu_sub(*fbc->counters, count); + __this_cpu_sub(*fbc->counters, count - amount); raw_spin_unlock_irqrestore(&fbc->lock, flags); } else { this_cpu_add(*fbc->counters, amount); -- cgit v1.2.3-70-g09d2