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Fix overflow of "running" value in getstat()

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It seems in some cases procs_running field of /proc/stat can contain 0 even if vmstat itself is running. At least this can be reproduced on Linux 3.9.3 compiled with BFS scheduler.

Since getstat() decrements value of procs_running by 1, we get overflow:

$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0 667732 918996  57376 911260   21   30    36    40   98   45 14 82  4  1
 4294967295  0 667728 916716  57376 911264    8    0     8     0 1958 3733 28  7 65  1
 0  0 667700 915996  57376 911416   24    0   152     0 1735 3600 23  5 71  1
 4294967295  0 667700 915872  57376 911392    0    0     0     0 1528 3165 21  4 76  0
This commit is contained in:
Vadim Ushakov 2013-06-11 12:09:05 +08:00
parent b55f9b97db
commit 5c9c7c8b1f
1 changed files with 2 additions and 1 deletions
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3
proc/sysinfo.c
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@ -494,7 +494,8 @@ void getstat(jiff *restrict cuse, jiff *restrict cice, jiff *restrict csys, jiff
getrunners(running, blocked); getrunners(running, blocked);
} }
(*running)--; // exclude vmstat itself if(*running)
(*running)--; // exclude vmstat itself
if(need_vmstat_file){ /* Linux 2.5.40-bk4 and above */ if(need_vmstat_file){ /* Linux 2.5.40-bk4 and above */
vminfo(); vminfo();