From: Jim Warner <james.warner@comcast.net>
Date: Sat, 17 Sep 2016 09:44:44 +0000 (-0500)
Subject: library: add priming read at 'new' time <most modules>
X-Git-Tag: v4.0.0~768
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1a2b62c7793f5f6865eec56a6f996e55495725bf;p=procps-ng

library: add priming read at 'new' time <most modules>

A priming read at 'new' time in that <slabinfo> module
was important so that permission problems are detected
early. Plus, it also had the potential of making delta
values valid when 'get' or 'select' were first called.

It is for that latter reason that such a read was also
incorporated in the <diskstats> module 'new' function.
No other module, however, employed such priming reads.

This patch just brings those potential benefits to all
of our other newlib modules with the exception of that
<pids> guy. That module is, of necessity, sufficiently
different from those others to justify such exclusion.

Not only are there precious few DELTA enums in <pids>,
but the costs of a priming read would be much greater.

[ otherwise, these newly added priming reads have no ]
[ measurable negative impact on performance/timings. ]

Signed-off-by: Jim Warner <james.warner@comcast.net>
---

diff --git a/proc/meminfo.c b/proc/meminfo.c
index 0882a493..53d4e46f 100644
--- a/proc/meminfo.c
+++ b/proc/meminfo.c
@@ -749,6 +749,14 @@ PROCPS_EXPORT int procps_meminfo_new (
         return rc;
     }
 
+    /* do a priming read here for the following potential benefits: |
+         1) ensure there will be no problems with subsequent access |
+         2) make delta results potentially useful, even if 1st time | */
+    if ((rc = meminfo_read_failed(p))) {
+        procps_meminfo_unref(&p);
+        return rc;
+    }
+
     *info = p;
     return 0;
 } // end: procps_meminfo_new
diff --git a/proc/stat.c b/proc/stat.c
index d81f817e..141873c7 100644
--- a/proc/stat.c
+++ b/proc/stat.c
@@ -828,6 +828,7 @@ PROCPS_EXPORT int procps_stat_new (
         struct stat_info **info)
 {
     struct stat_info *p;
+    int rc;
 
     if (info == NULL || *info != NULL)
         return -EINVAL;
@@ -869,6 +870,14 @@ PROCPS_EXPORT int procps_stat_new (
  #endif
 #endif
 
+    /* do a priming read here for the following potential benefits: |
+         1) ensure there will be no problems with subsequent access |
+         2) make delta results potentially useful, even if 1st time | */
+    if ((rc = stat_read_failed(p))) {
+        procps_stat_unref(&p);
+        return rc;
+    }
+
     *info = p;
     return 0;
 } // end :procps_stat_new
diff --git a/proc/vmstat.c b/proc/vmstat.c
index 62d480eb..71b374b5 100644
--- a/proc/vmstat.c
+++ b/proc/vmstat.c
@@ -1133,6 +1133,14 @@ PROCPS_EXPORT int procps_vmstat_new (
         return rc;
     }
 
+    /* do a priming read here for the following potential benefits: |
+         1) ensure there will be no problems with subsequent access |
+         2) make delta results potentially useful, even if 1st time | */
+    if ((rc = vmstat_read_failed(p))) {
+        procps_vmstat_unref(&p);
+        return rc;
+    }
+
     *info = p;
     return 0;
 } // end: procps_vmstat_new