LXR linux/drivers/misc/cxl/base.c

   1/*
   2 * Copyright 2014 IBM Corp.
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of the GNU General Public License
   6 * as published by the Free Software Foundation; either version
   7 * 2 of the License, or (at your option) any later version.
   8 */
   9
  10#include <linux/module.h>
  11#include <linux/rcupdate.h>
  12#include <asm/errno.h>
  13#include <misc/cxl.h>
  14#include "cxl.h"
  15
  16/* protected by rcu */
  17static struct cxl_calls *cxl_calls;
  18
  19atomic_t cxl_use_count = ATOMIC_INIT(0);
  20EXPORT_SYMBOL(cxl_use_count);
  21
  22#ifdef CONFIG_CXL_MODULE
  23
  24static inline struct cxl_calls *cxl_calls_get(void)
  25{
  26        struct cxl_calls *calls = NULL;
  27
  28        rcu_read_lock();
  29        calls = rcu_dereference(cxl_calls);
  30        if (calls && !try_module_get(calls->owner))
  31                calls = NULL;
  32        rcu_read_unlock();
  33
  34        return calls;
  35}
  36
  37static inline void cxl_calls_put(struct cxl_calls *calls)
  38{
  39        BUG_ON(calls != cxl_calls);
  40
  41        /* we don't need to rcu this, as we hold a reference to the module */
  42        module_put(cxl_calls->owner);
  43}
  44
  45#else /* !defined CONFIG_CXL_MODULE */
  46
  47static inline struct cxl_calls *cxl_calls_get(void)
  48{
  49        return cxl_calls;
  50}
  51
  52static inline void cxl_calls_put(struct cxl_calls *calls) { }
  53
  54#endif /* CONFIG_CXL_MODULE */
  55
  56void cxl_slbia(struct mm_struct *mm)
  57{
  58        struct cxl_calls *calls;
  59
  60        calls = cxl_calls_get();
  61        if (!calls)
  62                return;
  63
  64        if (cxl_ctx_in_use())
  65            calls->cxl_slbia(mm);
  66
  67        cxl_calls_put(calls);
  68}
  69
  70int register_cxl_calls(struct cxl_calls *calls)
  71{
  72        if (cxl_calls)
  73                return -EBUSY;
  74
  75        rcu_assign_pointer(cxl_calls, calls);
  76        return 0;
  77}
  78EXPORT_SYMBOL_GPL(register_cxl_calls);
  79
  80void unregister_cxl_calls(struct cxl_calls *calls)
  81{
  82        BUG_ON(cxl_calls->owner != calls->owner);
  83        RCU_INIT_POINTER(cxl_calls, NULL);
  84        synchronize_rcu();
  85}
  86EXPORT_SYMBOL_GPL(unregister_cxl_calls);
  87