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: 24+ 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
2010-01-08 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
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