srcu: Prevent cleanup_srcu_struct() from freeing non-dynamic ->sda
When an srcu_struct structure is created (but not in a kernel module) by DEFINE_SRCU() and friends, the per-CPU srcu_data structure is statically allocated. In all other cases, that structure is obtained from alloc_percpu(), in which case cleanup_srcu_struct() must invoke free_percpu() on the resulting ->sda pointer in the srcu_struct pointer. Which it does. Except that it also invokes free_percpu() on the ->sda pointer referencing the statically allocated per-CPU srcu_data structures. Which free_percpu() is surprisingly OK with. This commit nevertheless stops cleanup_srcu_struct() from freeing statically allocated per-CPU srcu_data structures. Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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@ -217,6 +217,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
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mutex_init(&ssp->srcu_barrier_mutex);
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atomic_set(&ssp->srcu_barrier_cpu_cnt, 0);
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INIT_DELAYED_WORK(&ssp->work, process_srcu);
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ssp->sda_is_static = is_static;
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if (!is_static)
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ssp->sda = alloc_percpu(struct srcu_data);
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if (!ssp->sda)
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@ -226,7 +227,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
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ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
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if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 1) {
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if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
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if (!is_static) {
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if (!ssp->sda_is_static) {
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free_percpu(ssp->sda);
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ssp->sda = NULL;
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return -ENOMEM;
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@ -446,8 +447,10 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
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rcu_seq_current(&ssp->srcu_gp_seq), ssp->srcu_gp_seq_needed);
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return; /* Caller forgot to stop doing call_srcu()? */
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}
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free_percpu(ssp->sda);
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ssp->sda = NULL;
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if (!ssp->sda_is_static) {
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free_percpu(ssp->sda);
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ssp->sda = NULL;
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}
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kfree(ssp->node);
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ssp->node = NULL;
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ssp->srcu_size_state = SRCU_SIZE_SMALL;
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