Currently, each CPU discovers the end of a given grace period on its own time, which is again good for efficiency but bad for fast grace periods, given that it is things like kfree() within the RCU callbacks that will cause trouble for pointers leaked from RCU read-side critical sections. This commit therefore uses on_each_cpu() to IPI each CPU after grace-period cleanup in order to inform each CPU of the end of the old grace period in a timely manner, but only in kernels build with CONFIG_RCU_STRICT_GRACE_PERIOD=y. Reported-by Jann Horn <jannh@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Showing the changes to kernel (1 of 1 file). Show all
Unified · Split
| @@ -2052,6 +2052,10 @@ static void rcu_gp_cleanup(void) · 2051 unmodified lines | ||
| 2052 | 2052 | rcu_state.gp_flags & RCU_GP_FLAG_INIT); |
| 2053 | 2053 | } |
| 2054 | 2054 | raw_spin_unlock_irq_rcu_node(rnp); |
| 2055 | + | |
| 2056 | + // If strict, make all CPUs aware of the end of the old grace period. | |
| 2057 | + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) | |
| 2058 | + on_each_cpu(rcu_strict_gp_boundary, NULL, 0); | |
| 2055 | 2059 | } |
| 2056 | 2060 | |
| 2057 | 2061 | /* |