diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2026-03-20 20:29:20 -0700 |
|---|---|---|
| committer | Boqun Feng <boqun@kernel.org> | 2026-03-25 08:59:02 -0700 |
| commit | 61bbcfb50514a8a94e035a7349697a3790ab4783 (patch) | |
| tree | 007c6b3cb9f770c1aa032fcb57c0a1d77d40b6a5 /kernel | |
| parent | 175b45ed343a9c547b5f45293d3ea08d38a7b6f4 (diff) | |
srcu: Push srcu_node allocation to GP when non-preemptible
When the srcutree.convert_to_big and srcutree.big_cpu_lim kernel boot
parameters specify initialization-time allocation of the srcu_node
tree for statically allocated srcu_struct structures (for example, in
DEFINE_SRCU() at build time instead of init_srcu_struct() at runtime),
init_srcu_struct_nodes() will attempt to dynamically allocate this tree
at the first run-time update-side use of this srcu_struct structure,
but while holding a raw spinlock. Because the memory allocator can
acquire non-raw spinlocks, this can result in lockdep splats.
This commit therefore uses the same SRCU_SIZE_ALLOC trick that is used
when the first run-time update-side use of this srcu_struct structure
happens before srcu_init() is called. The actual allocation then takes
place from workqueue context at the ends of upcoming SRCU grace periods.
[boqun: Adjust the sha1 of the Fixes tag]
Fixes: 175b45ed343a ("srcu: Use raw spinlocks so call_srcu() can be used under preempt_disable()")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/srcutree.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 2328827f8775..678bd9a73875 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -227,9 +227,12 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) ssp->srcu_sup->srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL; ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns(); if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) { - if (!init_srcu_struct_nodes(ssp, is_static ? GFP_ATOMIC : GFP_KERNEL)) + if (!preemptible()) + WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_ALLOC); + else if (init_srcu_struct_nodes(ssp, GFP_KERNEL)) + WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG); + else goto err_free_sda; - WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG); } ssp->srcu_sup->srcu_ssp = ssp; smp_store_release(&ssp->srcu_sup->srcu_gp_seq_needed, |