linux-kernel - Re: [RFC][PATCH] f2fs: Avoid print false deadlock messages.

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Date:	Wed, 15 May 2013 15:33:26 +0800
From:	majianpeng <majianpeng@...il.com>
To:	Libo Chen <clbchenlibo.chen@...wei.com>
CC:	Jaegeuk Kim <jaegeuk.kim@...sung.com>, peterz@...radead.org,
	mingo@...hat.com, linux-kernel <linux-kernel@...r.kernel.org>,
	linux-f2fs <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [RFC][PATCH] f2fs: Avoid print false deadlock messages.

On 05/15/2013 03:21 PM, Libo Chen wrote:
> On 2013/5/15 14:58, majianpeng wrote:
>> By adding some messages, i found this problem because the gcc
>> optimizing. For those codes:
>>>>        for (i = 0; i < NR_GLOBAL_LOCKS; i++)
>>>>                mutex_init(&sbi->fs_lock[i]);
>> The defination of mutex_init is:
>>>> #define mutex_init(mutex)
>>>> do {
>>>>
>>>>        static struct lock_class_key __key;
>>>>
>>>>                                                                      
>>>>        __mutex_init((mutex), #mutex, &__key);
>>>>
>>>> } while (0)
>> Because the optimizing of gcc, there are only one __key rather than
>> NR_GLOBAL_LOCKS times.
>>
>> Add there is other problems about lockname.Using 'for()' the lockname is
>> the same which is '&sbi->fs_lock[i]'.If it met problem about
>> mutex-operation, it can't find which one.
>>
>> Although my patch can work,i think it's not best.Because if
>> NR_GLOBAL_LOCKS changed, we may leak to change this.
>>
>> BTY, if who know how to avoid optimize, please tell me. Thanks!
>>
>> Signed-off-by: Jianpeng Ma <majianpeng@...il.com>
>> ---
>>  fs/f2fs/super.c | 13 ++++++++++---
>>  1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 8555f7d..ce08b96 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -520,7 +520,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>      struct buffer_head *raw_super_buf;
>>      struct inode *root;
>>      long err = -EINVAL;
>> -    int i;
>>  
>>      /* allocate memory for f2fs-specific super block info */
>>      sbi = kzalloc(sizeof(struct f2fs_sb_info), GFP_KERNEL);
>> @@ -578,8 +577,16 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>      mutex_init(&sbi->gc_mutex);
>>      mutex_init(&sbi->writepages);
>>      mutex_init(&sbi->cp_mutex);
>> -    for (i = 0; i < NR_GLOBAL_LOCKS; i++)
>> -        mutex_init(&sbi->fs_lock[i]);
>> +
>  you can try barrier() or mb()  to avoid compile optimization.
>
Hi,
    They aren't work!But thanks very much!

Thanks!
Jianpeng Ma
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