rt-patches/0174-idr-Use-local-lock-instead-of-preempt-enable-disable.patch

   1 From 7f536bd95b67f43531a225ed4e4f538f08eb2493 Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Tue, 14 Jul 2015 14:26:34 +0200
   4 Subject: [PATCH 174/366] idr: Use local lock instead of preempt enable/disable
   5
   6 We need to protect the per cpu variable and prevent migration.
   7
   8 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
   9 ---
  10  include/linux/idr.h |  4 ++++
  11  lib/idr.c           | 43 +++++++++++++++++++++++++++++++++++++------
  12  2 files changed, 41 insertions(+), 6 deletions(-)
  13
  14 diff --git a/include/linux/idr.h b/include/linux/idr.h
  15 index 013fd9b..f62be0a 100644
  16 --- a/include/linux/idr.h
  17 +++ b/include/linux/idr.h
  18 @@ -95,10 +95,14 @@ bool idr_is_empty(struct idr *idp);
  19   * Each idr_preload() should be matched with an invocation of this
  20   * function.  See idr_preload() for details.
  21   */
  22 +#ifdef CONFIG_PREEMPT_RT_FULL
  23 +void idr_preload_end(void);
  24 +#else
  25  static inline void idr_preload_end(void)
  26  {
  27         preempt_enable();
  28  }
  29 +#endif
  30
  31  /**
  32   * idr_find - return pointer for given id
  33 diff --git a/lib/idr.c b/lib/idr.c
  34 index 6098336..9decbe9 100644
  35 --- a/lib/idr.c
  36 +++ b/lib/idr.c
  37 @@ -30,6 +30,7 @@
  38  #include <linux/idr.h>
  39  #include <linux/spinlock.h>
  40  #include <linux/percpu.h>
  41 +#include <linux/locallock.h>
  42
  43  #define MAX_IDR_SHIFT          (sizeof(int) * 8 - 1)
  44  #define MAX_IDR_BIT            (1U << MAX_IDR_SHIFT)
  45 @@ -45,6 +46,37 @@ static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
  46  static DEFINE_PER_CPU(int, idr_preload_cnt);
  47  static DEFINE_SPINLOCK(simple_ida_lock);
  48
  49 +#ifdef CONFIG_PREEMPT_RT_FULL
  50 +static DEFINE_LOCAL_IRQ_LOCK(idr_lock);
  51 +
  52 +static inline void idr_preload_lock(void)
  53 +{
  54 +       local_lock(idr_lock);
  55 +}
  56 +
  57 +static inline void idr_preload_unlock(void)
  58 +{
  59 +       local_unlock(idr_lock);
  60 +}
  61 +
  62 +void idr_preload_end(void)
  63 +{
  64 +       idr_preload_unlock();
  65 +}
  66 +EXPORT_SYMBOL(idr_preload_end);
  67 +#else
  68 +static inline void idr_preload_lock(void)
  69 +{
  70 +       preempt_disable();
  71 +}
  72 +
  73 +static inline void idr_preload_unlock(void)
  74 +{
  75 +       preempt_enable();
  76 +}
  77 +#endif
  78 +
  79 +
  80  /* the maximum ID which can be allocated given idr->layers */
  81  static int idr_max(int layers)
  82  {
  83 @@ -115,14 +147,14 @@ static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
  84          * context.  See idr_preload() for details.
  85          */
  86         if (!in_interrupt()) {
  87 -               preempt_disable();
  88 +               idr_preload_lock();
  89                 new = __this_cpu_read(idr_preload_head);
  90                 if (new) {
  91                         __this_cpu_write(idr_preload_head, new->ary[0]);
  92                         __this_cpu_dec(idr_preload_cnt);
  93                         new->ary[0] = NULL;
  94                 }
  95 -               preempt_enable();
  96 +               idr_preload_unlock();
  97                 if (new)
  98                         return new;
  99         }
 100 @@ -366,7 +398,6 @@ static void idr_fill_slot(struct idr *idr, void *ptr, int id,
 101         idr_mark_full(pa, id);
 102  }
 103
 104 -
 105  /**
 106   * idr_preload - preload for idr_alloc()
 107   * @gfp_mask: allocation mask to use for preloading
 108 @@ -401,7 +432,7 @@ void idr_preload(gfp_t gfp_mask)
 109         WARN_ON_ONCE(in_interrupt());
 110         might_sleep_if(gfpflags_allow_blocking(gfp_mask));
 111
 112 -       preempt_disable();
 113 +       idr_preload_lock();
 114
 115         /*
 116          * idr_alloc() is likely to succeed w/o full idr_layer buffer and
 117 @@ -413,9 +444,9 @@ void idr_preload(gfp_t gfp_mask)
 118         while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
 119                 struct idr_layer *new;
 120
 121 -               preempt_enable();
 122 +               idr_preload_unlock();
 123                 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
 124 -               preempt_disable();
 125 +               idr_preload_lock();
 126                 if (!new)
 127                         break;
 128
 129 --
 130 1.9.1
 131