Subject: [merged] lib-percpu_counterc-fix-__percpu_counter_add.patch removed from -mm tree
To: tom.leiming@xxxxxxxxx,axboe@xxxxxxxxx,fan.du@xxxxxxxxxxxxx,paul.gortmaker@xxxxxxxxxxxxx,shli@xxxxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 15 Jan 2014 12:28:50 -0800
The patch titled
Subject: lib/percpu_counter.c: fix __percpu_counter_add()
has been removed from the -mm tree. Its filename was
lib-percpu_counterc-fix-__percpu_counter_add.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Ming Lei <tom.leiming@xxxxxxxxx>
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.
The patch fixes 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@xxxxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Fan Du <fan.du@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/percpu_counter.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN lib/percpu_counter.c~lib-percpu_counterc-fix-__percpu_counter_add lib/percpu_counter.c
--- a/lib/percpu_counter.c~lib-percpu_counterc-fix-__percpu_counter_add
+++ a/lib/percpu_counter.c
@@ -82,10 +82,10 @@ void __percpu_counter_add(struct percpu_
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();
}
_
Patches currently in -mm which might be from tom.leiming@xxxxxxxxx are
origin.patch
linux-next.patch
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