From: Paul E. McKenney Date: Fri, 24 Mar 2023 16:05:50 +0000 (-0700) Subject: srcu: Check for readers at module-exit time X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a7bf4d7c16c1cf9753873879630a5d5169eb3206;p=linux.git srcu: Check for readers at module-exit time If a given statically allocated in-module srcu_struct structure was ever used for updates, srcu_module_going() will invoke cleanup_srcu_struct() at module-exit time. This will check for the error case of SRCU readers persisting past module-exit time. On the other hand, if this srcu_struct structure never went through a grace period, srcu_module_going() only invokes free_percpu(), which would result in strange failures if SRCU readers persisted past module-exit time. This commit therefore adds a srcu_readers_active() check to srcu_module_going(), splatting if readers have persisted and refraining from invoking free_percpu() in that case. Better to leak memory than to suffer silent memory corruption! [ paulmck: Apply Zhang, Qiang1 feedback on memory leak. ] Tested-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 169a6513b7397..f9dd6ed5503ef 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1911,7 +1911,8 @@ static void srcu_module_going(struct module *mod) if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed)) && !WARN_ON_ONCE(!ssp->srcu_sup->sda_is_static)) cleanup_srcu_struct(ssp); - free_percpu(ssp->sda); + if (!WARN_ON(srcu_readers_active(ssp))) + free_percpu(ssp->sda); } }