From 74e72f894d56eb9d2e1218530c658e7d297e002b Mon Sep 17 00:00:00 2001
From: Ming Lei <tom.leiming@gmail.com>
Date: Tue, 14 Jan 2014 17:56:42 -0800
Subject: [PATCH] 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 <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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
lib/percpu_counter.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index 7473ee3b4ee7..1da85bb1bc07 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();
}
--
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