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| author | Paul E. McKenney <paulmck@kernel.org> | 2021-04-21 14:30:54 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-05-13 09:13:23 -0700 |
| commit | 76c8eaafe4f061f3790112842a2fbb297e4bea88 (patch) | |
| tree | 3f6feabd24c2677e9cafd06406183f7ff11abd41 /include/linux/rcupdate.h | |
| parent | 3d3a0d1b508dcc47e82b0e12cde6585bc088b0cc (diff) | |
| download | linux-76c8eaafe4f061f3790112842a2fbb297e4bea88.tar.bz2 | |
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
The xchg() and cmpxchg() functions are sometimes used to carry out RCU
updates. Unfortunately, this can result in sparse warnings for both
the old-value and new-value arguments, as well as for the return value.
The arguments can be dealt with using RCU_INITIALIZER():
old_p = xchg(&p, RCU_INITIALIZER(new_p));
But a sparse warning still remains due to assigning the __rcu pointer
returned from xchg to the (most likely) non-__rcu pointer old_p.
This commit therefore provides an unrcu_pointer() macro that strips
the __rcu. This macro can be used as follows:
old_p = unrcu_pointer(xchg(&p, RCU_INITIALIZER(new_p)));
Reported-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1199ffd305d1..b071d02a028a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -363,6 +363,20 @@ static inline void rcu_preempt_sleep_check(void) { } #define rcu_check_sparse(p, space) #endif /* #else #ifdef __CHECKER__ */ +/** + * unrcu_pointer - mark a pointer as not being RCU protected + * @p: pointer needing to lose its __rcu property + * + * Converts @p from an __rcu pointer to a __kernel pointer. + * This allows an __rcu pointer to be used with xchg() and friends. + */ +#define unrcu_pointer(p) \ +({ \ + typeof(*p) *_________p1 = (typeof(*p) *__force)(p); \ + rcu_check_sparse(p, __rcu); \ + ((typeof(*p) __force __kernel *)(_________p1)); \ +}) + #define __rcu_access_pointer(p, space) \ ({ \ typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ |