Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 15 Mar 2002 08:16:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 15 Mar 2002 08:16:37 -0500 Received: from www.deepbluesolutions.co.uk ([212.18.232.186]:56332 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id ; Fri, 15 Mar 2002 08:16:19 -0500 Date: Fri, 15 Mar 2002 13:16:12 +0000 From: Russell King To: linux-kernel@vger.kernel.org, Linus Torvalds , Marcelo Tosatti , davej@suse.de Subject: [PATCH] 2.4 and 2.5: remove Alt-Sysrq-L Message-ID: <20020315131612.C24984@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Linus, Marcelo, Dave, The following patch removes Alt-Sysrq-L and its associated hack to kill of PID1, the init process. This is a mis-feature. If PID1 is killed, the kernel immediately enters an infinite loop in the depths of do_exit() with interrupts disabled, completely locking the machine. Obviously you can only reach for the reset button or power switch after this, leaving you with dirty filesystems. This patch has appeared on LKML a couple of months ago. --- orig/drivers/char/sysrq.c Fri Mar 15 10:13:07 2002 +++ linux/drivers/char/sysrq.c Mon Mar 11 11:44:18 2002 @@ -284,24 +284,20 @@ /* signal sysrq helper function * Sends a signal to all user processes */ -static void send_sig_all(int sig, int even_init) +static void send_sig_all(int sig) { struct task_struct *p; for_each_task(p) { - if (p->mm) { /* Not swapper nor kernel thread */ - if (p->pid == 1 && even_init) - /* Ugly hack to kill init */ - p->pid = 0x8000; - if (p->pid != 1) - force_sig(sig, p); - } + if (p->mm && p->pid != 1) + /* Not swapper, init nor kernel thread */ + force_sig(sig, p); } } static void sysrq_handle_term(int key, struct pt_regs *pt_regs, struct kbd_struct *kbd, struct tty_struct *tty) { - send_sig_all(SIGTERM, 0); + send_sig_all(SIGTERM); console_loglevel = 8; } static struct sysrq_key_op sysrq_term_op = { @@ -312,7 +308,7 @@ static void sysrq_handle_kill(int key, struct pt_regs *pt_regs, struct kbd_struct *kbd, struct tty_struct *tty) { - send_sig_all(SIGKILL, 0); + send_sig_all(SIGKILL); console_loglevel = 8; } static struct sysrq_key_op sysrq_kill_op = { @@ -321,17 +317,6 @@ action_msg: "Kill All Tasks", }; -static void sysrq_handle_killall(int key, struct pt_regs *pt_regs, - struct kbd_struct *kbd, struct tty_struct *tty) { - send_sig_all(SIGKILL, 1); - console_loglevel = 8; -} -static struct sysrq_key_op sysrq_killall_op = { - handler: sysrq_handle_killall, - help_msg: "killalL", - action_msg: "Kill All Tasks (even init)", -}; - /* END SIGNAL SYSRQ HANDLERS BLOCK */ @@ -366,7 +351,7 @@ #else /* k */ NULL, #endif -/* l */ &sysrq_killall_op, +/* l */ NULL, /* m */ &sysrq_showmem_op, /* n */ NULL, /* o */ NULL, /* This will often be registered -- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html - 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/