Commit f4d01a25 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Use static init for statically allocated in-module srcu_struct 



Further shrinking the srcu_struct structure is eased by requiring
that in-module srcu_struct structures rely more heavily on static
initialization.  In particular, this preserves the property that
a module-load-time srcu_struct initialization can fail only due
to memory-allocation failure of the per-CPU srcu_data structures.
It might also slightly improve robustness by keeping the number of memory
allocations that must succeed down percpu_alloc() call.

This is in preparation for splitting an srcu_usage structure out
of the srcu_struct structure.

[ paulmck: Fold in qiang1.zhang@intel.com feedback. ]

Cc: Christoph Hellwig <hch@lst.de>
Tested-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Tested-by: default avatar"Zhang, Qiang1" <qiang1.zhang@intel.com>
Tested-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 3e67cb8a

include/linux/srcutree.h

+14 −5
Original line number Diff line number Diff line
@@ -108,15 +108,24 @@ struct srcu_struct { 
#define SRCU_STATE_SCAN1	1

#define SRCU_STATE_SCAN2	2



#define __SRCU_STRUCT_INIT(name, pcpu_name)							\

{												\

	.sda = &pcpu_name,									\

#define __SRCU_STRUCT_INIT_COMMON(name)								\

	.lock = __SPIN_LOCK_UNLOCKED(name.lock),						\

	.srcu_gp_seq_needed = -1UL,								\

	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),					\

	__SRCU_DEP_MAP_INIT(name)								\

	__SRCU_DEP_MAP_INIT(name)



#define __SRCU_STRUCT_INIT_MODULE(name)								\

{												\

	__SRCU_STRUCT_INIT_COMMON(name)								\

}



#define __SRCU_STRUCT_INIT(name, pcpu_name)							\

{												\

	.sda = &pcpu_name,									\

	__SRCU_STRUCT_INIT_COMMON(name)								\

}





/*

 * Define and initialize a srcu struct at build time.

 * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
@@ -138,7 +147,7 @@ struct srcu_struct { 
 */

#ifdef MODULE

# define __DEFINE_SRCU(name, is_static)								\

	is_static struct srcu_struct name;							\

	is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name);			\

	extern struct srcu_struct * const __srcu_struct_##name;					\

	struct srcu_struct * const __srcu_struct_##name						\

		__section("___srcu_struct_ptrs") = &name

kernel/rcu/srcutree.c

+13 −6
Original line number Diff line number Diff line
@@ -1873,13 +1873,14 @@ void __init srcu_init(void) 
static int srcu_module_coming(struct module *mod)

{

	int i;

	struct srcu_struct *ssp;

	struct srcu_struct **sspp = mod->srcu_struct_ptrs;

	int ret;



	for (i = 0; i < mod->num_srcu_structs; i++) {

		ret = init_srcu_struct(*(sspp++));

		if (WARN_ON_ONCE(ret))

			return ret;

		ssp = *(sspp++);

		ssp->sda = alloc_percpu(struct srcu_data);

		if (WARN_ON_ONCE(!ssp->sda))

			return -ENOMEM;

	}

	return 0;

}
@@ -1888,10 +1889,16 @@ static int srcu_module_coming(struct module *mod) 
static void srcu_module_going(struct module *mod)

{

	int i;

	struct srcu_struct *ssp;

	struct srcu_struct **sspp = mod->srcu_struct_ptrs;



	for (i = 0; i < mod->num_srcu_structs; i++)

		cleanup_srcu_struct(*(sspp++));

	for (i = 0; i < mod->num_srcu_structs; i++) {

		ssp = *(sspp++);

		if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq_needed)) &&

		    !WARN_ON_ONCE(!ssp->sda_is_static))

			cleanup_srcu_struct(ssp);

		free_percpu(ssp->sda);

	}

}



/* Handle one module, either coming or going. */