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bootchart: Ensure that /proc/schedstat is read entirely

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On multi-core systems file /proc/schedstat may be
larger than 4096 bytes and pread() will only read part of it.

Fix issue https://github.com/systemd/systemd/issues/404
This commit is contained in:
Gianpaolo Macario 2015-06-30 15:09:02 +00:00
parent 8914ea0e90
commit c91d0fd2f4
1 changed files with 8 additions and 22 deletions
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30
src/bootchart/store.c
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@ -37,6 +37,7 @@
#include "store.h"
#include "bootchart.h"
#include "cgroup-util.h"
#include "fileio.h"
/*
* Alloc a static 4k buffer for stdio - primarily used to increase
@ -97,13 +98,14 @@ int log_sample(DIR *proc,
int *cpus) {
static int vmstat = -1;
static int schedstat = -1;
_cleanup_free_ char *buf_schedstat = NULL;
char buf[4096];
char key[256];
char val[256];
char rt[256];
char wt[256];
char *m;
int r;
int c;
int p;
int mod;
@ -156,27 +158,13 @@ vmstat_next:
break;
}
if (schedstat < 0) {
/* overall CPU utilization */
schedstat = openat(procfd, "schedstat", O_RDONLY|O_CLOEXEC);
if (schedstat < 0)
return log_error_errno(errno, "Failed to open /proc/schedstat (requires CONFIG_SCHEDSTATS=y in kernel config): %m");
}
/* Parse "/proc/schedstat" for overall CPU utilization */
r = read_full_file("/proc/schedstat", &buf_schedstat, NULL);
if (r < 0)
return log_error_errno(r, "Unable to read schedstat: %m");
n = pread(schedstat, buf, sizeof(buf) - 1, 0);
if (n <= 0) {
schedstat = safe_close(schedstat);
if (n < 0)
return -errno;
return -ENODATA;
}
buf[n] = '\0';
m = buf;
m = buf_schedstat;
while (m) {
int r;
if (sscanf(m, "%s %*s %*s %*s %*s %*s %*s %s %s", key, rt, wt) < 3)
goto schedstat_next;
@ -238,7 +226,6 @@ schedstat_next:
_cleanup_fclose_ FILE *st = NULL;
char t[32];
struct ps_struct *parent;
int r;
ps->next_ps = new0(struct ps_struct, 1);
if (!ps->next_ps)
@ -427,7 +414,6 @@ schedstat_next:
return -errno;
}
FOREACH_DIRENT(ent, taskdir, break) {
int r;
int tid = -1;
_cleanup_close_ int tid_schedstat = -1;
long long delta_rt;