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srcu: Check for readers at module-exit time

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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) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2023-03-24 09:05:50 -07:00
parent fd1b3f8e09
commit a7bf4d7c16
1 changed files with 2 additions and 1 deletions
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3
kernel/rcu/srcutree.c
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@ -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);
}
}