Commit 16db3d3f authored by Heinrich Schuchardt's avatar Heinrich Schuchardt Committed by Linus Torvalds
Browse files

kernel/sysctl.c: threads-max observe limits 



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: default avatarHeinrich 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ac1b398d

include/linux/sysctl.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/fork.c

+29 −2
Original line number Diff line number Diff line
@@ -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;

}

kernel/sysctl.c

+2 −4
Original line number Diff line number Diff line
@@ -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",

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