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

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Message-ID: <51933770.4060607@huawei.com>
Date:	Wed, 15 May 2013 15:21:20 +0800
From:	Libo Chen <clbchenlibo.chen@...wei.com>
To:	majianpeng <majianpeng@...il.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 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.

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