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kernel/sysctl.c: threads-max observe limits

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Users can change the maximum number of threads by writing to
/proc/sys/kernel/threads-max.

With the patch the value entered is checked against the same limits that
apply when fork_init is called.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Heinrich Schuchardt 2015-04-16 12:47:50 -07:00 committed by Linus Torvalds
parent ac1b398de1
commit 16db3d3f11
3 changed files with 34 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
include/linux/sysctl.h
View file

@ -212,4 +212,7 @@ static inline void setup_sysctl_set(struct ctl_table_set *p,
#endif /* CONFIG_SYSCTL */
int sysctl_max_threads(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
#endif /* _LINUX_SYSCTL_H */

31
kernel/fork.c
View file

@ -74,6 +74,7 @@
#include <linux/uprobes.h>
#include <linux/aio.h>
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@ -266,7 +267,7 @@ void __init __weak arch_task_cache_init(void) { }
/*
* set_max_threads
*/
static void set_max_threads(void)
static void set_max_threads(unsigned int max_threads_suggested)
{
u64 threads;
@ -280,6 +281,9 @@ static void set_max_threads(void)
threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);
if (threads > max_threads_suggested)
threads = max_threads_suggested;
max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
}
@ -298,7 +302,7 @@ void __init fork_init(void)
/* do the arch specific task caches init */
arch_task_cache_init();
set_max_threads();
set_max_threads(MAX_THREADS);
init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
@ -2020,3 +2024,26 @@ int unshare_files(struct files_struct **displaced)
task_unlock(task);
return 0;
}
int sysctl_max_threads(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table t;
int ret;
int threads = max_threads;
int min = MIN_THREADS;
int max = MAX_THREADS;
t = *table;
t.data = &threads;
t.extra1 = &min;
t.extra2 = &max;
ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
if (ret || !write)
return ret;
set_max_threads(threads);
return 0;
}

6
kernel/sysctl.c
View file

@ -93,11 +93,9 @@
#include <linux/nmi.h>
#endif
#if defined(CONFIG_SYSCTL)
/* External variables not in a header file. */
extern int max_threads;
extern int suid_dumpable;
#ifdef CONFIG_COREDUMP
extern int core_uses_pid;
@ -710,10 +708,10 @@ static struct ctl_table kern_table[] = {
#endif
{
.procname = "threads-max",
.data = &max_threads,
.data = NULL,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
.proc_handler = sysctl_max_threads,
},
{
.procname = "random",