Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752544AbbBXVRK (ORCPT ); Tue, 24 Feb 2015 16:17:10 -0500 Received: from mail-ie0-f182.google.com ([209.85.223.182]:34927 "EHLO mail-ie0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750788AbbBXVRH (ORCPT ); Tue, 24 Feb 2015 16:17:07 -0500 Date: Tue, 24 Feb 2015 13:17:03 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Heinrich Schuchardt cc: Andrew Morton , Aaron Tomlin , Andy Lutomirski , Davidlohr Bueso , "David S. Miller" , Fabian Frederick , Guenter Roeck , "H. Peter Anvin" , Ingo Molnar , Jens Axboe , Joe Perches , Johannes Weiner , Kees Cook , Michael Marineau , Oleg Nesterov , "Paul E. McKenney" , Peter Zijlstra , Prarit Bhargava , Rik van Riel , Rusty Russell , Steven Rostedt , Thomas Gleixner , Vladimir Davydov , linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] kernel/sysctl.c: threads-max observe limits In-Reply-To: <1424806701-30099-4-git-send-email-xypron.glpk@gmx.de> Message-ID: References: <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> <1424806701-30099-1-git-send-email-xypron.glpk@gmx.de> <1424806701-30099-4-git-send-email-xypron.glpk@gmx.de> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3159 Lines: 107 On Tue, 24 Feb 2015, Heinrich Schuchardt wrote: > 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. > Correct me if I'm wrong, but this is a change in functionality (without update to Documentation/sysctl/kernel.txt which describes threads-max) since it does not allow the value to be lowered as before from the calculation involving totalram_pages. The value passed to set_max_threads() only caps the value. > Signed-off-by: Heinrich Schuchardt > --- > include/linux/sysctl.h | 3 +++ > kernel/fork.c | 24 ++++++++++++++++++++++++ > kernel/sysctl.c | 6 ++---- > 3 files changed, 29 insertions(+), 4 deletions(-) > > diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h > index b7361f8..795d5fe 100644 > --- a/include/linux/sysctl.h > +++ b/include/linux/sysctl.h > @@ -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 */ > diff --git a/kernel/fork.c b/kernel/fork.c > index 880c78d..52a07c7 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -74,6 +74,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -2024,3 +2025,26 @@ 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; > +} > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 137c7f6..2e195ae 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -92,11 +92,9 @@ > #include > #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; > @@ -709,10 +707,10 @@ 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", -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/