tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
1
fork

Configure Feed

Select the types of activity you want to include in your feed.

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>

authored by

Paul E. McKenney and committed by
Boqun Feng 61bbcfb5 175b45ed

+5 -2
+5 -2
kernel/rcu/srcutree.c
··· 227 227 ssp->srcu_sup->srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL; 228 228 ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns(); 229 229 if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) { 230 - if (!init_srcu_struct_nodes(ssp, is_static ? GFP_ATOMIC : GFP_KERNEL)) 230 + if (!preemptible()) 231 + WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_ALLOC); 232 + else if (init_srcu_struct_nodes(ssp, GFP_KERNEL)) 233 + WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG); 234 + else 231 235 goto err_free_sda; 232 - WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG); 233 236 } 234 237 ssp->srcu_sup->srcu_ssp = ssp; 235 238 smp_store_release(&ssp->srcu_sup->srcu_gp_seq_needed,