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Date: Wed, 23 Apr 2014 19:42:08 +0800
From: Hong zhi guo <honkiko@...il.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: Jet Chen <jet.chen@...el.com>,
Hong Zhiguo <zhiguohong@...cent.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [blk] WARNING: CPU: 0 PID: 300 at kernel/softirq.c:156 _local_bh_enable_ip()
Hi,
I think one fix is to use "_local_bh_enable()" instead of "local_bh_enable()"
in u64_stats_fetch_retry_bh(). There's no enabling of irq in
_local_bh_enable().
But I wonder why we do "WARN_ON_ONCE(!irqs_disabled()
)" in
_local_bh_enable()? What's the bad thing if someone call
_local_bh_enable() with irqs_diabled()?
Is below change acceptable?
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 490fcbb..f446763 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -142,9 +142,11 @@ EXPORT_SYMBOL(_local_bh_enable);
void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
{
+ unsigned long flags;
+
WARN_ON_ONCE(in_irq() || irqs_disabled());
#ifdef CONFIG_TRACE_IRQFLAGS
- local_irq_disable();
+ raw_local_irq_save(flags);
#endif
/*
* Are softirqs going to be turned on now:
@@ -167,7 +169,7 @@ void __local_bh_enable_ip(unsigned long ip,
unsigned int cnt)
preempt_count_dec();
#ifdef CONFIG_TRACE_IRQFLAGS
- local_irq_enable();
+ raw_local_irq_restore(flags);
#endif
preempt_check_resched();
}
Zhiguo
On Tue, Apr 22, 2014 at 9:06 AM, Jens Axboe <axboe@...nel.dk> wrote:
> On 2014-04-20 14:30, Jet Chen wrote:
>>
>> Hi Zhiguo,
>>
>> I got the below dmesg and the first bad commit is
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> commit 2c575026fae6e63771bd2a4c1d407214a8096a89
>> Author: Hong Zhiguo <zhiguohong@...cent.com>
>> AuthorDate: Wed Nov 20 10:35:05 2013 -0700
>> Commit: Jens Axboe <axboe@...nel.dk>
>> CommitDate: Wed Nov 20 15:33:04 2013 -0700
>>
>> Update of blkg_stat and blkg_rwstat may happen in bh context.
>> While u64_stats_fetch_retry is only preempt_disable on 32bit
>> UP system. This is not enough to avoid preemption by bh and
>> may read strange 64 bit value.
>> Signed-off-by: Hong Zhiguo <zhiguohong@...cent.com>
>> Acked-by: Tejun Heo <tj@...nel.org>
>> Cc: stable@...nel.org
>> Signed-off-by: Jens Axboe <axboe@...nel.dk>
>>
>>
>>
>>
>> +-----------------------------------------------------------+------------+------------+
>> | | 82023bb7f7 |
>> 2c575026fa |
>>
>> +-----------------------------------------------------------+------------+------------+
>> | boot_successes | 47 |
>> 0 |
>> | boot_failures | 13 |
>> 20 |
>> | BUG:kernel_boot_hang | 13 |
>> 5 |
>> | inconsistent_IN-SOFTIRQ-W-SOFTIRQ-ON-W_usage | 0 |
>> 15 |
>> | backtrace:smpboot_thread_fn | 0 |
>> 15 |
>> | backtrace:vfs_read | 0 |
>> 9 |
>> | backtrace:SyS_read | 0 |
>> 9 |
>> | WARNING:CPU:PID:at_kernel/softirq.c:_local_bh_enable_ip() | 0 |
>> 7 |
>> | BUG:spinlock_lockup_suspected_on_CPU | 0 |
>> 1 |
>> | backtrace:do_mount | 0 |
>> 6 |
>> | backtrace:SyS_mount | 0 |
>> 6 |
>> | backtrace:async_run_entry_fn | 0 |
>> 0 |
>>
>> +-----------------------------------------------------------+------------+------------+
>>
>> [ 12.318816] WARNING: CPU: 0 PID: 300 at kernel/softirq.c:156
>> _local_bh_enable_ip+0x34/0x97()
>
>
> Does this still happen with 3.15-rc2?
>
> --
> Jens Axboe
>
> --
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--
best regards
Hong Zhiguo
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