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| author | Paul E. McKenney <paulmck@kernel.org> | 2021-06-24 19:05:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-01-26 01:37:46 +0300 |
| commit | b1a07165be21ad9ab925ff0615bf991f47dcee00 (patch) | |
| tree | 3e7be0ada746b88f27975bb0bfe0840897fcbeed /include/linux | |
| parent | 1d1d5b90ea01c25bb8318a4667eefc77b628e609 (diff) | |
| download | linux-b1a07165be21ad9ab925ff0615bf991f47dcee00.tar.xz | |
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
[ Upstream commit 76c8eaafe4f061f3790112842a2fbb297e4bea88 ]
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>
Stable-dep-of: 5f35a624c1e3 ("drm/nouveau/fence:: fix warning directly dereferencing a rcu pointer")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/linux')
| -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 ef8d56b18da6..8716a1706351 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -366,6 +366,20 @@ 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); \ |