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x86, percpu: Add 'percpu_read_stable()' interface for cacheable accesses

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This is very useful for some common things like 'get_current()' and
'get_thread_info()', which can be used multiple times in a function, and
where the result is cacheable.

tj: Added the magical undocumented "P" modifier to UP __percpu_arg()
    to force gcc to dereference the pointer value passed in via the
    "p" input constraint.  Without this, percpu_read_stable() returns
    the address of the percpu variable.  Also added comment explaining
    the difference between percpu_read() and percpu_read_stable().

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Linus Torvalds
2009-08-03 14:08:48 +09:00
committed by Tejun Heo
parent a33a052f19
commit ed8d9adf35
3 changed files with 21 additions and 9 deletions
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2
arch/x86/include/asm/current.h
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@@ -11,7 +11,7 @@ DECLARE_PER_CPU(struct task_struct *, current_task);
static __always_inline struct task_struct *get_current(void)
{
return percpu_read(current_task);
return percpu_read_stable(current_task);
}
#define current get_current()