From: ebiederm@xmission.com (Eric W. Biederman)
To: Andi Kleen <andi@firstfloor.org>
Cc: paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [4/9] SYSCTL: Use RCU strings for core_pattern sysctl
Date: Mon, 04 Jan 2010 22:56:59 -0800 [thread overview]
Message-ID: <m1zl4t82f8.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <20100105021529.205EFB17C2@basil.firstfloor.org> (Andi Kleen's message of "Tue\, 5 Jan 2010 03\:15\:29 +0100 \(CET\)")
Andi Kleen <andi@firstfloor.org> writes:
> Also saves ~220 bytes in the data segment for default kernels.
>
> As a bonus this removes one use of the BKL.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> ---
> fs/exec.c | 11 +++++------
> kernel/sysctl.c | 6 +++---
> 2 files changed, 8 insertions(+), 9 deletions(-)
>
> Index: linux-2.6.33-rc2-ak/fs/exec.c
> ===================================================================
> --- linux-2.6.33-rc2-ak.orig/fs/exec.c
> +++ linux-2.6.33-rc2-ak/fs/exec.c
> @@ -62,7 +62,7 @@
> #include "internal.h"
>
> int core_uses_pid;
> -char core_pattern[CORENAME_MAX_SIZE] = "core";
> +char *core_pattern = "core";
> unsigned int core_pipe_limit;
> int suid_dumpable = 0;
>
> @@ -1421,7 +1421,7 @@ EXPORT_SYMBOL(set_binfmt);
> static int format_corename(char *corename, long signr)
> {
> const struct cred *cred = current_cred();
> - const char *pat_ptr = core_pattern;
> + const char *pat_ptr = rcu_dereference(core_pattern);
rcu_dereference should aways be between rcu_read_lock()
and rcu_read_unlock();
> int ispipe = (*pat_ptr == '|');
> char *out_ptr = corename;
> char *const out_end = corename + CORENAME_MAX_SIZE;
> @@ -1825,12 +1825,11 @@ void do_coredump(long signr, int exit_co
> clear_thread_flag(TIF_SIGPENDING);
>
> /*
> - * lock_kernel() because format_corename() is controlled by sysctl, which
> - * uses lock_kernel()
> + * Protect corename by RCU vs proc_rcu_string()
> */
> - lock_kernel();
> + rcu_read_lock();
> ispipe = format_corename(corename, signr);
> - unlock_kernel();
> + rcu_read_unlock();
>
> if ((!ispipe) && (cprm.limit < binfmt->min_coredump))
> goto fail_unlock;
> Index: linux-2.6.33-rc2-ak/kernel/sysctl.c
> ===================================================================
> --- linux-2.6.33-rc2-ak.orig/kernel/sysctl.c
> +++ linux-2.6.33-rc2-ak/kernel/sysctl.c
> @@ -75,7 +75,7 @@ extern int sysctl_oom_dump_tasks;
> extern int max_threads;
> extern int core_uses_pid;
> extern int suid_dumpable;
> -extern char core_pattern[];
> +extern char *core_pattern;
> extern unsigned int core_pipe_limit;
> extern int pid_max;
> extern int min_free_kbytes;
> @@ -399,10 +399,10 @@ static struct ctl_table kern_table[] = {
> },
> {
> .procname = "core_pattern",
> - .data = core_pattern,
> + .data = &core_pattern,
> .maxlen = CORENAME_MAX_SIZE,
> .mode = 0644,
> - .proc_handler = proc_dostring,
> + .proc_handler = proc_rcu_string,
> },
> {
> .procname = "core_pipe_limit",
next prev parent reply other threads:[~2010-01-05 6:57 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-05 2:15 [PATCH] [0/9] SYSCTL: Use RCU to avoid races with string sysctls v2 Andi Kleen
2010-01-05 2:15 ` [PATCH] [1/9] Add rcustring ADT for RCU protected strings v2 Andi Kleen
2010-01-05 5:32 ` Paul E. McKenney
2010-01-05 10:47 ` Andi Kleen
2010-01-05 14:11 ` Paul E. McKenney
2010-01-05 14:19 ` Andi Kleen
2010-01-08 23:50 ` Andrew Morton
2010-01-11 12:12 ` Bert Wesarg
2010-01-11 14:26 ` Andi Kleen
2010-01-05 2:15 ` [PATCH] [2/9] Add a kernel_address() that works for data too Andi Kleen
2010-01-05 8:44 ` Russell King
2010-01-05 8:58 ` Sam Ravnborg
2010-01-05 19:04 ` Russell King
2010-01-05 19:15 ` Andi Kleen
2010-01-05 19:15 ` Andi Kleen
2010-01-08 23:51 ` Andrew Morton
2010-01-05 2:15 ` [PATCH] [3/9] SYSCTL: Add proc_rcu_string to manage sysctls using rcu strings Andi Kleen
2010-01-05 2:15 ` [PATCH] [4/9] SYSCTL: Use RCU strings for core_pattern sysctl Andi Kleen
2010-01-05 6:56 ` Eric W. Biederman [this message]
2010-01-05 11:49 ` Andi Kleen
2010-01-05 2:15 ` [PATCH] [5/9] SYSCTL: Add call_usermodehelper_cleanup() Andi Kleen
2010-01-05 2:15 ` [PATCH] [6/9] SYSCTL: Convert modprobe_path to proc_rcu_string() Andi Kleen
2010-01-05 2:15 ` [PATCH] [7/9] SYSCTL: Convert poweroff_command to proc_rcu_string Andi Kleen
2010-01-05 2:15 ` [PATCH] [8/9] SYSCTL: Convert hotplug helper string to proc_rcu_string() Andi Kleen
2010-01-05 2:15 ` [PATCH] [9/9] SYSCTL: Use RCU protected sysctl for ocfs group add helper Andi Kleen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=m1zl4t82f8.fsf@fess.ebiederm.org \
--to=ebiederm@xmission.com \
--cc=akpm@linux-foundation.org \
--cc=andi@firstfloor.org \
--cc=linux-kernel@vger.kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.