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Date: Sat, 8 Nov 2008 13:10:54 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Ken Chen <kenchen@...gle.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace
* Ken Chen <kenchen@...gle.com> wrote:
> On Fri, Nov 7, 2008 at 12:32 AM, Ingo Molnar <mingo@...e.hu> wrote:
> > oh well - Ken, could you please switch it to seqfiles?
>
> On Fri, Nov 7, 2008 at 12:49 AM, Alexey Dobriyan wrote:
> > Or you can do all of this in ->show(), without start/next/stop:
> >
> > for (i = 0; i < N; i++)
> > seq_printf(m, "[<%p>] %pS\n", x, x);
>
> Here is a patch convert to seq_file using proc_single_show() helper.
> I don't see it to be any superior than what was before using
> snprintf(). seq_read also allocate one page for printf buffer, so
> functionally it is the same (perhaps a little bit better because it
> can use the whole page, compare to PROC_BLOCK_SIZE currently).
> Ingo, it's your call whether to merge this patch or not.
>
> I also agree that using full blown seqfile start/show/stop won't add
> value because most valuable stack at the top are already printed.
Well, it removes 2 lines of code and makes the iteration slightly more
resilient (as there's no 'ret' value to be maintained anymore), so
i've applied your patch to tip/core/stacktrace - thanks Ken! (see the
commit below)
Sidenote: it would still be nice if the procfs folks converted the
old-style code there to the new seqfile APIs, before requiring
everyone _else_ to follow those guidelines?
Ingo
----------------->
>From 35f0b5fd7fab907a1119eaa614d9b24e5e225755 Mon Sep 17 00:00:00 2001
From: Ken Chen <kenchen@...gle.com>
Date: Fri, 7 Nov 2008 10:38:04 -0800
Subject: [PATCH] stacktrace: convert /proc/<pid>/stack to seqfiles
Here is a patch convert to seq_file using proc_single_show() helper.
Signed-off-by: Ken Chen <kenchen@...gle.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
fs/proc/base.c | 16 +++++++---------
1 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 805e514..6d294a4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -351,11 +351,12 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer)
#define MAX_STACK_TRACE_DEPTH 64
-static int proc_pid_stack(struct task_struct *task, char *buffer)
+static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
{
struct stack_trace trace;
unsigned long *entries;
- int i, len = 0;
+ int i;
entries = kmalloc(sizeof(*entries)*MAX_STACK_TRACE_DEPTH, GFP_KERNEL);
if (!entries)
@@ -375,15 +376,12 @@ static int proc_pid_stack(struct task_struct *task, char *buffer)
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;
+ seq_printf(m, "[<%p>] %pS\n",
+ (void *)entries[i], (void *)entries[i]);
}
kfree(entries);
- return len;
+ return 0;
}
#endif
@@ -2537,7 +2535,7 @@ static const struct pid_entry tgid_base_stuff[] = {
INF("wchan", S_IRUGO, pid_wchan),
#endif
#ifdef CONFIG_STACKTRACE
- INF("stack", S_IRUSR, pid_stack),
+ ONE("stack", S_IRUSR, pid_stack),
#endif
#ifdef CONFIG_SCHEDSTATS
INF("schedstat", S_IRUGO, pid_schedstat),
--
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