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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include "alloc-util.h"
#include "def.h"
#include "fd-util.h"
#include "fileio.h"
#include "parse-util.h"
#include "process-util.h"
#include "procfs-util.h"
#include "stdio-util.h"
#include "string-util.h"
int procfs_tasks_get_limit(uint64_t *ret) {
_cleanup_free_ char *value = NULL;
uint64_t pid_max, threads_max;
int r;
assert(ret);
/* So there are two sysctl files that control the system limit of processes:
*
* 1. kernel.threads-max: this is probably the sysctl that makes more sense, as it directly puts a limit on
* concurrent tasks.
*
* 2. kernel.pid_max: this limits the numeric range PIDs can take, and thus indirectly also limits the number
* of concurrent threads. AFAICS it's primarily a compatibility concept: some crappy old code used a signed
* 16bit type for PIDs, hence the kernel provides a way to ensure the PIDs never go beyond INT16_MAX by
* default.
*
* By default #2 is set to much lower values than #1, hence the limit people come into contact with first, as
* it's the lowest boundary they need to bump when they want higher number of processes.
*
* Also note the weird definition of #2: PIDs assigned will be kept below this value, which means the number of
* tasks that can be created is one lower, as PID 0 is not a valid process ID. */
r = read_one_line_file("/proc/sys/kernel/pid_max", &value);
if (r < 0)
return r;
r = safe_atou64(value, &pid_max);
if (r < 0)
return r;
value = mfree(value);
r = read_one_line_file("/proc/sys/kernel/threads-max", &value);
if (r < 0)
return r;
r = safe_atou64(value, &threads_max);
if (r < 0)
return r;
/* Subtract one from pid_max, since PID 0 is not a valid PID */
*ret = MIN(pid_max-1, threads_max);
return 0;
}
int procfs_tasks_set_limit(uint64_t limit) {
char buffer[DECIMAL_STR_MAX(uint64_t)+1];
_cleanup_free_ char *value = NULL;
uint64_t pid_max;
int r;
if (limit == 0) /* This makes no sense, we are userspace and hence count as tasks too, and we want to live,
* hence the limit conceptually has to be above 0. Also, most likely if anyone asks for a zero
* limit he/she probably means "no limit", hence let's better refuse this to avoid
* confusion. */
return -EINVAL;
/* The Linux kernel doesn't allow this value to go below 20, hence don't allow this either, higher values than
* TASKS_MAX are not accepted by the pid_max sysctl. We'll treat anything this high as "unbounded" and hence
* set it to the maximum. */
limit = CLAMP(limit, 20U, TASKS_MAX);
r = read_one_line_file("/proc/sys/kernel/pid_max", &value);
if (r < 0)
return r;
r = safe_atou64(value, &pid_max);
if (r < 0)
return r;
/* As pid_max is about the numeric pid_t range we'll bump it if necessary, but only ever increase it, never
* decrease it, as threads-max is the much more relevant sysctl. */
if (limit > pid_max-1) {
sprintf(buffer, "%" PRIu64, limit+1); /* Add one, since PID 0 is not a valid PID */
r = write_string_file("/proc/sys/kernel/pid_max", buffer, WRITE_STRING_FILE_DISABLE_BUFFER);
if (r < 0)
return r;
}
sprintf(buffer, "%" PRIu64, limit);
r = write_string_file("/proc/sys/kernel/threads-max", buffer, WRITE_STRING_FILE_DISABLE_BUFFER);
if (r < 0) {
uint64_t threads_max;
/* Hmm, we couldn't write this? If so, maybe it was already set properly? In that case let's not
* generate an error */
value = mfree(value);
if (read_one_line_file("/proc/sys/kernel/threads-max", &value) < 0)
return r; /* return original error */
if (safe_atou64(value, &threads_max) < 0)
return r; /* return original error */
if (MIN(pid_max-1, threads_max) != limit)
return r; /* return original error */
/* Yay! Value set already matches what we were trying to set, hence consider this a success. */
}
return 0;
}
int procfs_tasks_get_current(uint64_t *ret) {
_cleanup_free_ char *value = NULL;
const char *p, *nr;
size_t n;
int r;
assert(ret);
r = read_one_line_file("/proc/loadavg", &value);
if (r < 0)
return r;
/* Look for the second part of the fourth field, which is separated by a slash from the first part. None of the
* earlier fields use a slash, hence let's use this to find the right spot. */
p = strchr(value, '/');
if (!p)
return -EINVAL;
p++;
n = strspn(p, DIGITS);
nr = strndupa(p, n);
return safe_atou64(nr, ret);
}
static uint64_t calc_gcd64(uint64_t a, uint64_t b) {
while (b > 0) {
uint64_t t;
t = a % b;
a = b;
b = t;
}
return a;
}
int procfs_cpu_get_usage(nsec_t *ret) {
_cleanup_free_ char *first_line = NULL;
unsigned long user_ticks, nice_ticks, system_ticks, irq_ticks, softirq_ticks,
guest_ticks = 0, guest_nice_ticks = 0;
long ticks_per_second;
uint64_t sum, gcd, a, b;
const char *p;
int r;
assert(ret);
r = read_one_line_file("/proc/stat", &first_line);
if (r < 0)
return r;
p = first_word(first_line, "cpu");
if (!p)
return -EINVAL;
if (sscanf(p, "%lu %lu %lu %*u %*u %lu %lu %*u %lu %lu",
&user_ticks,
&nice_ticks,
&system_ticks,
&irq_ticks,
&softirq_ticks,
&guest_ticks,
&guest_nice_ticks) < 5) /* we only insist on the first five fields */
return -EINVAL;
ticks_per_second = sysconf(_SC_CLK_TCK);
if (ticks_per_second < 0)
return -errno;
assert(ticks_per_second > 0);
sum = (uint64_t) user_ticks + (uint64_t) nice_ticks + (uint64_t) system_ticks +
(uint64_t) irq_ticks + (uint64_t) softirq_ticks +
(uint64_t) guest_ticks + (uint64_t) guest_nice_ticks;
/* Let's reduce this fraction before we apply it to avoid overflows when converting this to µsec */
gcd = calc_gcd64(NSEC_PER_SEC, ticks_per_second);
a = (uint64_t) NSEC_PER_SEC / gcd;
b = (uint64_t) ticks_per_second / gcd;
*ret = DIV_ROUND_UP((nsec_t) sum * (nsec_t) a, (nsec_t) b);
return 0;
}
int procfs_memory_get_current(uint64_t *ret) {
uint64_t mem_total = UINT64_MAX, mem_free = UINT64_MAX;
_cleanup_fclose_ FILE *f = NULL;
int r;
assert(ret);
f = fopen("/proc/meminfo", "re");
if (!f)
return -errno;
for (;;) {
_cleanup_free_ char *line = NULL;
uint64_t *v;
char *p, *e;
size_t n;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return r;
if (r == 0)
return -EINVAL; /* EOF: Couldn't find one or both fields? */
p = first_word(line, "MemTotal:");
if (p)
v = &mem_total;
else {
p = first_word(line, "MemFree:");
if (p)
v = &mem_free;
else
continue;
}
/* Determine length of numeric value */
n = strspn(p, DIGITS);
if (n == 0)
return -EINVAL;
e = p + n;
/* Ensure the line ends in " kB" */
n = strspn(e, WHITESPACE);
if (n == 0)
return -EINVAL;
if (!streq(e + n, "kB"))
return -EINVAL;
*e = 0;
r = safe_atou64(p, v);
if (r < 0)
return r;
if (*v == UINT64_MAX)
return -EINVAL;
if (mem_total != UINT64_MAX && mem_free != UINT64_MAX)
break;
}
if (mem_free > mem_total)
return -EINVAL;
*ret = (mem_total - mem_free) * 1024U;
return 0;
}
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