queue-6.1/s390-pai_ext-replace-atomic_t-with-refcount_t.patch

   1 From 117b4dfc411cc5896e800a18ff9469c9f9db7da2 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Thu, 27 Apr 2023 10:33:31 +0200
   4 Subject: s390/pai_ext: replace atomic_t with refcount_t
   5
   6 From: Thomas Richter <tmricht@linux.ibm.com>
   7
   8 [ Upstream commit 1f2597cd3686955a4d64e01909dbfe625a2a35a1 ]
   9
  10 The s390 PMU of PAI extension 1 NNPA counters uses atomic_t for
  11 reference counting. Replace this with the proper data type
  12 refcount_t.
  13
  14 No functional change.
  15
  16 Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
  17 Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
  18 Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
  19 Stable-dep-of: e9f3af02f639 ("s390/pai: fix sampling event removal for PMU device driver")
  20 Signed-off-by: Sasha Levin <sashal@kernel.org>
  21 ---
  22  arch/s390/kernel/perf_pai_ext.c | 23 +++++++++++++----------
  23  1 file changed, 13 insertions(+), 10 deletions(-)
  24
  25 diff --git a/arch/s390/kernel/perf_pai_ext.c b/arch/s390/kernel/perf_pai_ext.c
  26 index b4d89654183a2..d6bc919530143 100644
  27 --- a/arch/s390/kernel/perf_pai_ext.c
  28 +++ b/arch/s390/kernel/perf_pai_ext.c
  29 @@ -56,7 +56,7 @@ struct paiext_map {
  30         struct pai_userdata *save;      /* Area to store non-zero counters */
  31         enum paiext_mode mode;          /* Type of event */
  32         unsigned int active_events;     /* # of PAI Extension users */
  33 -       unsigned int refcnt;
  34 +       refcount_t refcnt;
  35         struct perf_event *event;       /* Perf event for sampling */
  36         struct paiext_cb *paiext_cb;    /* PAI extension control block area */
  37  };
  38 @@ -66,14 +66,14 @@ struct paiext_mapptr {
  39  };
  40
  41  static struct paiext_root {            /* Anchor to per CPU data */
  42 -       int refcnt;                     /* Overall active events */
  43 +       refcount_t refcnt;              /* Overall active events */
  44         struct paiext_mapptr __percpu *mapptr;
  45  } paiext_root;
  46
  47  /* Free per CPU data when the last event is removed. */
  48  static void paiext_root_free(void)
  49  {
  50 -       if (!--paiext_root.refcnt) {
  51 +       if (refcount_dec_and_test(&paiext_root.refcnt)) {
  52                 free_percpu(paiext_root.mapptr);
  53                 paiext_root.mapptr = NULL;
  54         }
  55 @@ -86,7 +86,7 @@ static void paiext_root_free(void)
  56   */
  57  static int paiext_root_alloc(void)
  58  {
  59 -       if (++paiext_root.refcnt == 1) {
  60 +       if (!refcount_inc_not_zero(&paiext_root.refcnt)) {
  61                 /* The memory is already zeroed. */
  62                 paiext_root.mapptr = alloc_percpu(struct paiext_mapptr);
  63                 if (!paiext_root.mapptr) {
  64 @@ -97,6 +97,7 @@ static int paiext_root_alloc(void)
  65                          */
  66                         return -ENOMEM;
  67                 }
  68 +               refcount_set(&paiext_root.refcnt, 1);
  69         }
  70         return 0;
  71  }
  72 @@ -128,7 +129,7 @@ static void paiext_event_destroy(struct perf_event *event)
  73
  74         mutex_lock(&paiext_reserve_mutex);
  75         cpump->event = NULL;
  76 -       if (!--cpump->refcnt)           /* Last reference gone */
  77 +       if (refcount_dec_and_test(&cpump->refcnt))      /* Last reference gone */
  78                 paiext_free(mp);
  79         paiext_root_free();
  80         mutex_unlock(&paiext_reserve_mutex);
  81 @@ -169,7 +170,7 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
  82                 rc = -ENOMEM;
  83                 cpump = kzalloc(sizeof(*cpump), GFP_KERNEL);
  84                 if (!cpump)
  85 -                       goto unlock;
  86 +                       goto undo;
  87
  88                 /* Allocate memory for counter area and counter extraction.
  89                  * These are
  90 @@ -189,8 +190,9 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
  91                                              GFP_KERNEL);
  92                 if (!cpump->save || !cpump->area || !cpump->paiext_cb) {
  93                         paiext_free(mp);
  94 -                       goto unlock;
  95 +                       goto undo;
  96                 }
  97 +               refcount_set(&cpump->refcnt, 1);
  98                 cpump->mode = a->sample_period ? PAI_MODE_SAMPLING
  99                                                : PAI_MODE_COUNTER;
 100         } else {
 101 @@ -201,15 +203,15 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 102                 if (cpump->mode == PAI_MODE_SAMPLING ||
 103                     (cpump->mode == PAI_MODE_COUNTER && a->sample_period)) {
 104                         rc = -EBUSY;
 105 -                       goto unlock;
 106 +                       goto undo;
 107                 }
 108 +               refcount_inc(&cpump->refcnt);
 109         }
 110
 111         rc = 0;
 112         cpump->event = event;
 113 -       ++cpump->refcnt;
 114
 115 -unlock:
 116 +undo:
 117         if (rc) {
 118                 /* Error in allocation of event, decrement anchor. Since
 119                  * the event in not created, its destroy() function is never
 120 @@ -217,6 +219,7 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 121                  */
 122                 paiext_root_free();
 123         }
 124 +unlock:
 125         mutex_unlock(&paiext_reserve_mutex);
 126         /* If rc is non-zero, no increment of counter/sampler was done. */
 127         return rc;
 128 --
 129 2.43.0
 130