From patchwork Wed Jul 15 20:39:32 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Russell King X-Patchwork-Id: 6800541 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 5C2BAC05AC for ; Wed, 15 Jul 2015 20:43:09 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4C83B20665 for ; Wed, 15 Jul 2015 20:43:07 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E628A2065D for ; Wed, 15 Jul 2015 20:43:03 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZFTTG-0001jQ-DV; Wed, 15 Jul 2015 20:40:02 +0000 Received: from pandora.arm.linux.org.uk ([2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZFTTC-0001fV-IA for linux-arm-kernel@lists.infradead.org; Wed, 15 Jul 2015 20:39:59 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=arm.linux.org.uk; s=pandora-2014; h=Date:Sender:Message-Id:Content-Type:Content-Transfer-Encoding:MIME-Version:Subject:Cc:To:From:References:In-Reply-To; bh=eMpDj4+w/Kl43ant73x5C33py/FM/eYB7HlRrls3LYU=; b=htYt+2FxE8BmHgyvtDAi3/WiHlrBV/zhZhU9S9Sy0lt4Yd1Guhi9B5JNYDXkyH+H8KOY5MpzZnzUd8Xvh7Vfo7rFqTIrvLomgLmM0pL+XzZezA6nEhTMSJgwTWwzfPFnua4eExFiDC+qs//8/HFzNyeqGD3UIM89lggyvzpsea0=; Received: from e0022681537dd.dyn.arm.linux.org.uk ([2001:4d48:ad52:3201:222:68ff:fe15:37dd]:49062 helo=rmk-PC.arm.linux.org.uk) by pandora.arm.linux.org.uk with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1ZFTSn-0005zD-1h; Wed, 15 Jul 2015 21:39:33 +0100 Received: from rmk by rmk-PC.arm.linux.org.uk with local (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1ZFTSm-0006uz-3s; Wed, 15 Jul 2015 21:39:32 +0100 In-Reply-To: <20150715203911.GF7557@n2100.arm.linux.org.uk> References: <20150715203911.GF7557@n2100.arm.linux.org.uk> From: Russell King To: linux-arm-kernel@lists.infradead.org,x86@kernel.org Subject: [PATCH 1/3] nmi: create generic NMI backtrace implementation MIME-Version: 1.0 Content-Disposition: inline Message-Id: Date: Wed, 15 Jul 2015 21:39:32 +0100 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150715_133959_052482_CC6C7E9B X-CRM114-Status: GOOD ( 26.06 ) X-Spam-Score: -3.4 (---) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Thompson , linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.5 required=5.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,RP_MATCHES_RCVD,T_DKIM_INVALID,UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP x86s NMI backtrace implementation (for arch_trigger_all_cpu_backtrace()) is fairly generic in nature - the only architecture specific bits are the act of raising the NMI to other CPUs, and reporting the status of the NMI handler. These are fairly simple to factor out, and produce a generic implementation which can be shared between ARM and x86. Signed-off-by: Russell King Reviewed-by: Thomas Gleixner --- include/linux/nmi.h | 6 ++ lib/Makefile | 2 +- lib/nmi_backtrace.c | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 169 insertions(+), 1 deletion(-) create mode 100644 lib/nmi_backtrace.c diff --git a/include/linux/nmi.h b/include/linux/nmi.h index f94da0e65dea..5791e3229068 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -49,6 +49,12 @@ static inline bool trigger_allbutself_cpu_backtrace(void) arch_trigger_all_cpu_backtrace(false); return true; } + +/* generic implementation */ +void nmi_trigger_all_cpu_backtrace(bool include_self, + void (*raise)(cpumask_t *mask)); +bool nmi_cpu_backtrace(struct pt_regs *regs); + #else static inline bool trigger_all_cpu_backtrace(void) { diff --git a/lib/Makefile b/lib/Makefile index 6897b527581a..392169c5bc4e 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ sha1.o md5.o irq_regs.o argv_split.o \ proportions.o flex_proportions.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ - earlycpio.o seq_buf.o + earlycpio.o seq_buf.o nmi_backtrace.o obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o lib-$(CONFIG_MMU) += ioremap.o diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c new file mode 100644 index 000000000000..88d3d32e5923 --- /dev/null +++ b/lib/nmi_backtrace.c @@ -0,0 +1,162 @@ +/* + * NMI backtrace support + * + * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King, + * with the following header: + * + * HW NMI watchdog support + * + * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. + * + * Arch specific calls to support NMI watchdog + * + * Bits copied from original nmi.c file + */ +#include +#include +#include +#include +#include + +#ifdef arch_trigger_all_cpu_backtrace +/* For reliability, we're prepared to waste bits here. */ +static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; +static cpumask_t printtrace_mask; + +#define NMI_BUF_SIZE 4096 + +struct nmi_seq_buf { + unsigned char buffer[NMI_BUF_SIZE]; + struct seq_buf seq; +}; + +/* Safe printing in NMI context */ +static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq); + +/* "in progress" flag of arch_trigger_all_cpu_backtrace */ +static unsigned long backtrace_flag; + +static void print_seq_line(struct nmi_seq_buf *s, int start, int end) +{ + const char *buf = s->buffer + start; + + printk("%.*s", (end - start) + 1, buf); +} + +void nmi_trigger_all_cpu_backtrace(bool include_self, + void (*raise)(cpumask_t *mask)) +{ + struct nmi_seq_buf *s; + int i, cpu, this_cpu = get_cpu(); + + if (test_and_set_bit(0, &backtrace_flag)) { + /* + * If there is already a trigger_all_cpu_backtrace() in progress + * (backtrace_flag == 1), don't output double cpu dump infos. + */ + put_cpu(); + return; + } + + cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask); + if (!include_self) + cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); + + cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask)); + + /* + * Set up per_cpu seq_buf buffers that the NMIs running on the other + * CPUs will write to. + */ + for_each_cpu(cpu, to_cpumask(backtrace_mask)) { + s = &per_cpu(nmi_print_seq, cpu); + seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE); + } + + if (!cpumask_empty(to_cpumask(backtrace_mask))) { + pr_info("Sending NMI to %s CPUs:\n", + (include_self ? "all" : "other")); + raise(to_cpumask(backtrace_mask)); + } + + /* Wait for up to 10 seconds for all CPUs to do the backtrace */ + for (i = 0; i < 10 * 1000; i++) { + if (cpumask_empty(to_cpumask(backtrace_mask))) + break; + mdelay(1); + touch_softlockup_watchdog(); + } + + /* + * Now that all the NMIs have triggered, we can dump out their + * back traces safely to the console. + */ + for_each_cpu(cpu, &printtrace_mask) { + int len, last_i = 0; + + s = &per_cpu(nmi_print_seq, cpu); + len = seq_buf_used(&s->seq); + if (!len) + continue; + + /* Print line by line. */ + for (i = 0; i < len; i++) { + if (s->buffer[i] == '\n') { + print_seq_line(s, last_i, i); + last_i = i + 1; + } + } + /* Check if there was a partial line. */ + if (last_i < len) { + print_seq_line(s, last_i, len - 1); + pr_cont("\n"); + } + } + + clear_bit(0, &backtrace_flag); + smp_mb__after_atomic(); + put_cpu(); +} + +/* + * It is not safe to call printk() directly from NMI handlers. + * It may be fine if the NMI detected a lock up and we have no choice + * but to do so, but doing a NMI on all other CPUs to get a back trace + * can be done with a sysrq-l. We don't want that to lock up, which + * can happen if the NMI interrupts a printk in progress. + * + * Instead, we redirect the vprintk() to this nmi_vprintk() that writes + * the content into a per cpu seq_buf buffer. Then when the NMIs are + * all done, we can safely dump the contents of the seq_buf to a printk() + * from a non NMI context. + */ +static int nmi_vprintk(const char *fmt, va_list args) +{ + struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); + unsigned int len = seq_buf_used(&s->seq); + + seq_buf_vprintf(&s->seq, fmt, args); + return seq_buf_used(&s->seq) - len; +} + +bool nmi_cpu_backtrace(struct pt_regs *regs) +{ + int cpu = smp_processor_id(); + + if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { + printk_func_t printk_func_save = this_cpu_read(printk_func); + + /* Replace printk to write into the NMI seq */ + this_cpu_write(printk_func, nmi_vprintk); + pr_warn("NMI backtrace for cpu %d\n", cpu); + show_regs(regs); + this_cpu_write(printk_func, printk_func_save); + + cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); + return true; + } + + return false; +} +NOKPROBE_SYMBOL(nmi_cpu_backtrace); +#endif