Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753233AbYKGH7q (ORCPT ); Fri, 7 Nov 2008 02:59:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751039AbYKGH7h (ORCPT ); Fri, 7 Nov 2008 02:59:37 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:34819 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbYKGH7g (ORCPT ); Fri, 7 Nov 2008 02:59:36 -0500 Date: Fri, 7 Nov 2008 08:59:25 +0100 From: Ingo Molnar To: Alexey Dobriyan , Andrew Morton Cc: Ken Chen , linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace Message-ID: <20081107075925.GA1825@elte.hu> References: <20081106203520.GD3578@elte.hu> <20081107003021.GA18666@google.com> <20081107004824.GA28780@x200.localdomain> <20081107074147.GA26607@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081107074147.GA26607@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5395 Lines: 168 * Ingo Molnar wrote: > > > + * buffer size used for proc read. See proc_info_read(). > > > + * 4K page size but our output routines use some slack for overruns > > > + */ > > > +#define PROC_BLOCK_SIZE (3*1024) > > That sounds like a proper limit - the hard limit for this particular > printout function is 4096-170, so we are well within the > PROC_BLOCK_SIZE range. ok, i've added Ken's patch to tip/core/stacktrace and started testing it. Alexey, i've added your Acked-by because you appeared to like the patch - let me know if i should remove it. i've done a few finishing touches to the patch as well - see the end result below. Andrew, i remember that you found some sort of problem (crashes?) with stack-dumping tasks that are running on another CPU (or something like that) - do you remember the specifics? Could we run into any of those problems with the patch below, on some rare architecture? Ingo -------------------> >From d3d23f82adeb5ec8a9546747d1df058dcaad0589 Mon Sep 17 00:00:00 2001 From: Ken Chen Date: Thu, 6 Nov 2008 16:30:23 -0800 Subject: [PATCH] stacktrace: add /proc//stack to dump task's stack trace Impact: add the new (root-only) /proc//stack debug facility This patch adds the ability to query a task's current stack trace via /proc//stack. It is considered to be more useful than /proc/pid/wchan as it provides full stack trace instead of single depth. It is also more useful than sysrq-t because it does not overflow the dmesg like sysrq-t often does, can be read in a finegrained per-task way and can be read programmatically as well. It works on sleeping and running tasks as well. Also, move up PROC_BLOCK_SIZE a bit so that proc_pid_stack() can use it. [ mingo@elte.hu: small cleanups, comments ] Signed-off-by: Ken Chen Acked-by: Alexey Dobriyan Signed-off-by: Ingo Molnar --- Documentation/filesystems/proc.txt | 1 + fs/proc/base.c | 52 ++++++++++++++++++++++++++++++++++- 2 files changed, 51 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index bcceb99..11f5b75 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -139,6 +139,7 @@ Table 1-1: Process specific entries in /proc statm Process memory status information status Process status in human readable form wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan + stack Report full stack trace, enable via CONFIG_STACKTRACE smaps Extension based on maps, the rss size for each mapped file .............................................................................. diff --git a/fs/proc/base.c b/fs/proc/base.c index 486cf3f..805e514 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -65,6 +65,7 @@ #include #include #include +#include #include #include #include @@ -130,6 +131,12 @@ struct pid_entry { { .proc_show = &proc_##OTYPE } ) /* + * buffer size used for proc read. See proc_info_read(). + * 4K page size but our output routines use some slack for overruns + */ +#define PROC_BLOCK_SIZE (3*1024) + +/* * Count the number of hardlinks for the pid_entry table, excluding the . * and .. links. */ @@ -340,6 +347,46 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer) } #endif /* CONFIG_KALLSYMS */ +#ifdef CONFIG_STACKTRACE + +#define MAX_STACK_TRACE_DEPTH 64 + +static int proc_pid_stack(struct task_struct *task, char *buffer) +{ + struct stack_trace trace; + unsigned long *entries; + int i, len = 0; + + entries = kmalloc(sizeof(*entries)*MAX_STACK_TRACE_DEPTH, GFP_KERNEL); + if (!entries) + return -ENOMEM; + + trace.nr_entries = 0; + trace.max_entries = MAX_STACK_TRACE_DEPTH; + trace.entries = entries; + trace.skip = 0; + + /* + * Protect against the task exiting (and deallocating its + * stack, etc.) while we save its backtrace: + */ + read_lock(&tasklist_lock); + save_stack_trace_tsk(task, &trace); + read_unlock(&tasklist_lock); + + for (i = 0; i < trace.nr_entries; i++) { + len += snprintf(buffer + len, PROC_BLOCK_SIZE - len, + "[<%p>] %pS\n", + (void *)entries[i], (void *)entries[i]); + if (!len) + break; + } + kfree(entries); + + return len; +} +#endif + #ifdef CONFIG_SCHEDSTATS /* * Provides /proc/PID/schedstat @@ -688,8 +735,6 @@ static const struct file_operations proc_mountstats_operations = { .release = mounts_release, }; -#define PROC_BLOCK_SIZE (3*1024) /* 4K page size but our output routines use some slack for overruns */ - static ssize_t proc_info_read(struct file * file, char __user * buf, size_t count, loff_t *ppos) { @@ -2491,6 +2536,9 @@ static const struct pid_entry tgid_base_stuff[] = { #ifdef CONFIG_KALLSYMS INF("wchan", S_IRUGO, pid_wchan), #endif +#ifdef CONFIG_STACKTRACE + INF("stack", S_IRUSR, pid_stack), +#endif #ifdef CONFIG_SCHEDSTATS INF("schedstat", S_IRUGO, pid_schedstat), #endif -- 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/