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authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>2014-11-10 09:29:29 +1030
committerRusty Russell <rusty@rustcorp.com.au>2014-11-11 17:07:46 +1030
commit2f35c41f58a978dfa44ffa102249d556caa99eeb (patch)
tree871fdf31787639112af15e3532bb6617660f2e47 /kernel/module.c
parent0286b5ea125e58b4797747f688949c05394412e8 (diff)
downloadlinux-2f35c41f58a978dfa44ffa102249d556caa99eeb.tar.bz2
module: Replace module_ref with atomic_t refcnt
Replace module_ref per-cpu complex reference counter with an atomic_t simple refcnt. This is for code simplification. Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'kernel/module.c')
-rw-r--r--kernel/module.c39
1 files changed, 5 insertions, 34 deletions
diff --git a/kernel/module.c b/kernel/module.c
index d596a306b0a1..b1d485df5ac1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -631,15 +631,11 @@ EXPORT_TRACEPOINT_SYMBOL(module_get);
/* Init the unload section of the module. */
static int module_unload_init(struct module *mod)
{
- mod->refptr = alloc_percpu(struct module_ref);
- if (!mod->refptr)
- return -ENOMEM;
-
INIT_LIST_HEAD(&mod->source_list);
INIT_LIST_HEAD(&mod->target_list);
/* Hold reference count during initialization. */
- raw_cpu_write(mod->refptr->incs, 1);
+ atomic_set(&mod->refcnt, 1);
return 0;
}
@@ -721,8 +717,6 @@ static void module_unload_free(struct module *mod)
kfree(use);
}
mutex_unlock(&module_mutex);
-
- free_percpu(mod->refptr);
}
#ifdef CONFIG_MODULE_FORCE_UNLOAD
@@ -772,28 +766,7 @@ static int try_stop_module(struct module *mod, int flags, int *forced)
unsigned long module_refcount(struct module *mod)
{
- unsigned long incs = 0, decs = 0;
- int cpu;
-
- for_each_possible_cpu(cpu)
- decs += per_cpu_ptr(mod->refptr, cpu)->decs;
- /*
- * ensure the incs are added up after the decs.
- * module_put ensures incs are visible before decs with smp_wmb.
- *
- * This 2-count scheme avoids the situation where the refcount
- * for CPU0 is read, then CPU0 increments the module refcount,
- * then CPU1 drops that refcount, then the refcount for CPU1 is
- * read. We would record a decrement but not its corresponding
- * increment so we would see a low count (disaster).
- *
- * Rare situation? But module_refcount can be preempted, and we
- * might be tallying up 4096+ CPUs. So it is not impossible.
- */
- smp_rmb();
- for_each_possible_cpu(cpu)
- incs += per_cpu_ptr(mod->refptr, cpu)->incs;
- return incs - decs;
+ return (unsigned long)atomic_read(&mod->refcnt);
}
EXPORT_SYMBOL(module_refcount);
@@ -935,7 +908,7 @@ void __module_get(struct module *module)
{
if (module) {
preempt_disable();
- __this_cpu_inc(module->refptr->incs);
+ atomic_inc(&module->refcnt);
trace_module_get(module, _RET_IP_);
preempt_enable();
}
@@ -950,7 +923,7 @@ bool try_module_get(struct module *module)
preempt_disable();
if (likely(module_is_live(module))) {
- __this_cpu_inc(module->refptr->incs);
+ atomic_inc(&module->refcnt);
trace_module_get(module, _RET_IP_);
} else
ret = false;
@@ -965,9 +938,7 @@ void module_put(struct module *module)
{
if (module) {
preempt_disable();
- smp_wmb(); /* see comment in module_refcount */
- __this_cpu_inc(module->refptr->decs);
-
+ atomic_dec(&module->refcnt);
trace_module_put(module, _RET_IP_);
preempt_enable();
}