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-base.h>
  14 #include "cxl.h"
  15
  16 /* protected by rcu */
  17 static struct cxl_calls *cxl_calls;
  18
  19 atomic_t cxl_use_count = ATOMIC_INIT(0);
  20 EXPORT_SYMBOL(cxl_use_count);
  21
  22 #ifdef CONFIG_CXL_MODULE
  23
  24 static 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
  37 static 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
  47 static inline struct cxl_calls *cxl_calls_get(void)
  48 {
  49         return cxl_calls;
  50 }
  51
  52 static inline void cxl_calls_put(struct cxl_calls *calls) { }
  53
  54 #endif /* CONFIG_CXL_MODULE */
  55
  56 void 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
  70 int 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 }
  78 EXPORT_SYMBOL_GPL(register_cxl_calls);
  79
  80 void 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 }
  86 EXPORT_SYMBOL_GPL(unregister_cxl_calls);