Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261210AbUFCGeP (ORCPT ); Thu, 3 Jun 2004 02:34:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261231AbUFCGeP (ORCPT ); Thu, 3 Jun 2004 02:34:15 -0400 Received: from smtp810.mail.sc5.yahoo.com ([66.163.170.80]:5776 "HELO smtp810.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261210AbUFCGeH (ORCPT ); Thu, 3 Jun 2004 02:34:07 -0400 From: Dmitry Torokhov To: linux-kernel@vger.kernel.org Subject: [RFC] Changing SysRq - show registers handling Date: Thu, 3 Jun 2004 01:34:01 -0500 User-Agent: KMail/1.6.2 Cc: Andrew Morton , Greg KH , Vojtech Pavlik MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <200406030134.04121.dtor_core@ameritech.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3772 Lines: 123 Hi, Currently SysRq "show registers" command dumps registers and the call trace from keyboard interrupt context when SysRq-P. For that struct pt_regs * has to be dragged throughout entire input and USB systems. Other than passing this pointer to SysRq handler these systems has no interest in it, it is completely foreign piece of data for them and I would like to get rid of it. I am suggesting slightly changing semantics of SysRq-P handling - instread of dumping registers and call trace immediately it will simply post a request for this information to be dumped. When next HW interrupt arrives and is handled, before running softirqs then current stack trace will be printed. This approach adds small overhead to the HW interrupt handling routine as the condition has to be checked with every interrupt but I expect it to be negligible as it is only check and conditional jump that is almost never taken. The code should be hot in cache so branch prediction should work just fine. The patch below implements proposed changes in SysRq handler and adds necessary changes to do_IRQ() on i386. If it is agreed upon I will adjust other arches. Please let me know what you think. -- Dmitry ===== include/linux/sysrq.h 1.6 vs edited ===== --- 1.6/include/linux/sysrq.h 2004-05-15 01:11:58 -05:00 +++ edited/include/linux/sysrq.h 2004-06-01 00:29:09 -05:00 @@ -33,6 +33,17 @@ void __handle_sysrq(int, struct pt_regs *, struct tty_struct *); /* + * Check whether register dump has been requested and print it + */ +extern unsigned int sysrq_register_dump_requested; +void __sysrq_show_registers(struct pt_regs *); +static inline void sysrq_show_registers(struct pt_regs *pt_regs) +{ + if (unlikely(sysrq_register_dump_requested != 0)) + __sysrq_show_registers(pt_regs); +} + +/* * Sysrq registration manipulation functions */ @@ -76,6 +87,10 @@ } #else + +static inline void sysrq_show_registes(struct pt_regs *pt_regs) +{ +} static inline int __reterr(void) { ===== drivers/char/sysrq.c 1.30 vs edited ===== --- 1.30/drivers/char/sysrq.c 2004-05-15 01:11:58 -05:00 +++ edited/drivers/char/sysrq.c 2004-06-01 00:29:08 -05:00 @@ -135,12 +135,33 @@ /* SHOW SYSRQ HANDLERS BLOCK */ +unsigned int sysrq_register_dump_requested; +static spinlock_t show_registers_lock = SPIN_LOCK_UNLOCKED; + +void __sysrq_show_registers(struct pt_regs *pt_regs) +{ + unsigned long flags; + int doit = 0; + + spin_lock_irqsave(&show_registers_lock, flags); + if (sysrq_register_dump_requested) { + sysrq_register_dump_requested--; + doit = 1; + } + spin_unlock_irqrestore(&show_registers_lock, flags); + + if (doit) + show_regs(pt_regs); +} static void sysrq_handle_showregs(int key, struct pt_regs *pt_regs, struct tty_struct *tty) { - if (pt_regs) - show_regs(pt_regs); + unsigned long flags; + + spin_lock_irqsave(&show_registers_lock, flags); + sysrq_register_dump_requested++; + spin_unlock_irqrestore(&show_registers_lock, flags); } static struct sysrq_key_op sysrq_showregs_op = { .handler = sysrq_handle_showregs, ===== arch/i386/kernel/irq.c 1.53 vs edited ===== --- 1.53/arch/i386/kernel/irq.c 2004-05-29 02:26:35 -05:00 +++ edited/arch/i386/kernel/irq.c 2004-06-01 00:29:06 -05:00 @@ -34,6 +34,7 @@ #include #include #include +#include #include #include @@ -567,6 +568,8 @@ */ desc->handler->end(irq); spin_unlock(&desc->lock); + + sysrq_show_registers(®s); irq_exit(); - 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/