Commit a7bf4d7c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent fd1b3f8e

kernel/rcu/srcutree.c

+2 −1
Original line number Diff line number Diff line
@@ -1911,6 +1911,7 @@ 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);

		if (!WARN_ON(srcu_readers_active(ssp)))

			free_percpu(ssp->sda);

	}

}