Date: Mon, 14 Feb 2011 15:25:00 -0800 (PST)
Message-Id: <20110214.152500.104069812.davem@davemloft.net>
To: mathieu.desnoyers@polymtl.ca
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Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates
From: David Miller <davem@davemloft.net>
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From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Mon, 14 Feb 2011 18:03:01 -0500

> If this is true, then we have bugs in lots of xchg/cmpxchg users (which
> do not reside in atomic.h), e.g.:
> 
> fs/fs_struct.c:
> int current_umask(void)
> {
>         return current->fs->umask;
> }
> EXPORT_SYMBOL(current_umask);
> 
> kernel/sys.c:
> SYSCALL_DEFINE1(umask, int, mask)
> {
>         mask = xchg(&current->fs->umask, mask & S_IRWXUGO);
>         return mask;
> }
> 
> The solution to this would be to force all xchg/cmpxchg users to swap to
> atomic.h variables, which would force the ll semantic on read. But I'd
> really like to see where this is documented first -- or which PowerPC
> engineer we should talk to.

We can't wholesale to atomic_t because we do this on variables of
all sizes, not just 32-bit ones.

We do them on pointers in the networking for example.
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