gpu: nvgpu: minor cleanups in cyclestats snapshots

There are two minor cleanups of cyclestats snapshots code implemented:

1. In case of unacceptably small buffer passed as a cyclestats snapshot
   it causes a kernel panic during list element removal:
   NvRmGpuTest_Channel_Cyclestats_Snapshot_Gen for 1 clients,
	each has 4 KB mappings and 1 perfmons
   [  304.533073] Unable to handle kernel NULL .... address 00000008
   [  304.541825] pgd = ffffffc04fc9f000
   [  304.545277] [00000008] *pgd=0000000000000000
   [  304.549554] Internal error: Oops: 96000045 [#1] PREEMPT SMPa
   ....
   [  304.584978] PC is at css_gr_free_client_data+0x28/0xe4
   [  304.590105] LR is at gr_gk20a_css_attach+0x6e0/0x700

2. Also fix with improved allocation of perfmon IDs implemented.

Bug 1573150

Change-Id: I58b753434141bf573463563fdd699c11ea914943
Signed-off-by: Leonid Moiseichuk <lmoiseichuk@nvidia.com>
Reviewed-on: http://git-master/r/751385
(cherry picked from commit e9314c29df3fb708a20fff58cfa64c2ead857b0f)
Reviewed-on: http://git-master/r/753275
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/css_gr_gk20a.c b/drivers/gpu/nvgpu/gk20a/css_gr_gk20a.c
index 7509acd7..e8da54fb 100644
--- a/drivers/gpu/nvgpu/gk20a/css_gr_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/css_gr_gk20a.c
@@ -504,12 +504,17 @@ static u32 css_gr_allocate_perfmon_ids(struct gk20a_cs_snapshot *data,
         if (!count || count > CSS_MAX_PERFMON_IDS - CSS_FIRST_PERFMON_ID)
                 return 0;
 
-        for (f = CSS_FIRST_PERFMON_ID; f < e; f++) {
-                u32 slots = 0;
+        for (f = CSS_FIRST_PERFMON_ID; f <= e; f++) {
+                u32 slots;
                 u32 cur;
-                u32 end = f + count;
+                u32 end;
+
+                if (CSS_PERFMON_GET(pids, f))
+                        continue;
 
                 /* lookup for continuous hole [f, f+count) of unused bits */
+                slots = 0;
+                end = f + count;
                 for (cur = f; cur < end; cur++) {
                         if (CSS_PERFMON_GET(pids, cur))
                                 break;
@@ -556,7 +561,9 @@ static int css_gr_free_client_data(struct gk20a_cs_snapshot *data,
 {
         int ret = 0;
 
-        list_del(&client->list);
+        if (client->list.next && client->list.prev)
+                list_del(&client->list);
+
         if (client->perfmon_start && client->perfmon_count) {
                 if (client->perfmon_count != css_gr_release_perfmon_ids(data,
                                 client->perfmon_start, client->perfmon_count))