This commit does a compile-time check for rcu_assign_pointer() of NULL, and uses WRITE_ONCE() rather than smp_store_release() in that case.
Reported-by: Christoph Hellwig <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- include/linux/rcupdate.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index c61b6b9506e7..9be61e47badc 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -650,7 +650,16 @@ static inline void rcu_preempt_sleep_check(void) * please be careful when making changes to rcu_assign_pointer() and the * other macros that it invokes. */ -#define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v)) +#define rcu_assign_pointer(p, v) \ +({ \ + uintptr_t _r_a_p__v = (uintptr_t)(v); \ + \ + if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \ + WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \ + else \ + smp_store_release(&p, RCU_INITIALIZER((typeof(p))_r_a_p__v)); \ + _r_a_p__v; \ +}) /** * rcu_access_pointer() - fetch RCU pointer with no dereferencing -- 2.5.2
