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library: become more tolerant of /proc/cpuinfo formats

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In the issue referenced below, it is now apparent that
not all architectures follow a logical/expected format
for the /proc/cpuinfo file. Specifically, the expected
empty line after each processor entry might be missing
under some architectures for the last processor shown.

[ and a belated review of kernel source confirms it. ]

So this commit makes our stat module a little bit more
tolerant of some potential missing newline characters.

[ along the way, it's also now tolerant of a missing ]
[ cpuinfo file plus more efficient whenever a cpu is ]
[ is not linked to a core or toggled offline/online. ]

Reference(s):
https://gitlab.com/procps-ng/procps/-/issues/272
procps-ng/procps#272

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2023-03-01 00:00:00 -06:00 committed by Craig Small
parent 8c81808de0
commit 133a833942
1 changed files with 17 additions and 11 deletions
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24
library/stat.c
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@ -515,8 +515,9 @@ static int stat_cores_verify (
int a_cpu, a_core;
FILE *fp;
// be tolerant of a missing CORE_FILE ...
if (!(fp = fopen(CORE_FILE, "r")))
return 0;
return 1;
for (;;) {
if (NULL == fgets(buf, sizeof(buf), fp))
break;
@ -525,12 +526,11 @@ static int stat_cores_verify (
continue;
sscanf(buf, "processor : %d", &a_cpu);
for (;;) {
if (NULL == fgets(buf, sizeof(buf), fp)) {
fclose(fp);
errno = EIO;
return 0;
}
if (buf[0] == '\n') { /* Entry for specific processor is finished */
// be tolerant of missing empty line on last processor entry ...
if (NULL == fgets(buf, sizeof(buf), fp))
goto wrap_up;
// be tolerant of a missing 'core id' on any processor entry ...
if (buf[0] == '\n') {
a_core = a_cpu;
break;
}
@ -545,6 +545,7 @@ static int stat_cores_verify (
return 0;
}
}
wrap_up:
fclose(fp);
stat_cores_check(info);
return 1;
@ -785,6 +786,8 @@ reap_em_again:
cpu_ptr = info->cpus.hist.tics + i; // adapt to relocated if reap_em_again
do {
static int once_sw;
bp = 1 + strchr(bp, '\n');
// remember this cpu from last time around
memcpy(&cpu_ptr->old, &cpu_ptr->new, sizeof(struct stat_jifs));
@ -806,14 +809,17 @@ reap_em_again:
}
stat_derive_unique(cpu_ptr);
// force a one time core link for cpu0 (if possible) ...
if (!once_sw)
once_sw = cpu_ptr->saved_id = -1;
/* this happens if cpus are taken offline/brought back online
so we better force the proper current core association ... */
if (cpu_ptr->saved_id != cpu_ptr->id) {
cpu_ptr->saved_id = cpu_ptr->id;
cpu_ptr->core = NULL;
}
if (!cpu_ptr->core)
stat_cores_link(info, cpu_ptr);
}
#ifdef CPU_IDLE_FORCED
// first time through (that priming read) sum_ptr->edge will be zero |