linux-kernel - Re: [PATCH] lockdep: Avoid /proc/lockdep & lock

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Message-ID: <20071009040401.GA3493@tpepper-t42p.dolavim.us>
Date:	Mon, 8 Oct 2007 21:04:02 -0700
From:	Tim Pepper <lnxninja@...ux.vnet.ibm.com>
To:	Al Viro <viro@....linux.org.uk>
Cc:	Tim Pepper <lnxninja@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockdep: Avoid /proc/lockdep & lock_stat infinite
	output

On Tue 09 Oct at 02:30:11 +0100 viro@....linux.org.uk said:
> On Mon, Oct 08, 2007 at 06:15:51PM -0700, Tim Pepper wrote:
> > 
> > -	if (&class->lock_entry == all_lock_classes.next)
> > +	if (*pos == 0)
> >  		seq_printf(m, "all lock classes:\n");
> 
> Do not generate output outside of ->show() and you won't have these
> problems.  That's where your infinite output crap comes from.
> 
> IOW, NAK - fix the underlying problem.

Aaah...OK.  Can we add something like the following then:




Document that output must only come from _show() and SEQ_START_TOKEN is how
a _start() indicates a header is to be printed.

Signed-off-by: Tim Pepper <lnxninja@...ux.vnet.ibm.com>
Cc: Al Viro <viro@....linux.org.uk>

---

--- linux-2.6.orig/include/linux/seq_file.h
+++ linux-2.6.23-rc9/include/linux/seq_file.h
@@ -36,9 +36,10 @@ ssize_t seq_read(struct file *, char __u
 loff_t seq_lseek(struct file *, loff_t, int);
 int seq_release(struct inode *, struct file *);
 int seq_escape(struct seq_file *, const char *, const char *);
+
+/* these may only be called from a (*show) function */
 int seq_putc(struct seq_file *m, char c);
 int seq_puts(struct seq_file *m, const char *s);
-
 int seq_printf(struct seq_file *, const char *, ...)
 	__attribute__ ((format (printf,2,3)));
 
@@ -48,6 +49,11 @@ int single_open(struct file *, int (*)(s
 int single_release(struct inode *, struct file *);
 int seq_release_private(struct inode *, struct file *);
 
+/*
+ * return SEQ_START_TOKEN in your (*start) function and test for
+ * (v == SEQ_START_TOKEN) in * your (*show) funtion in order to
+ * print a header before your seq data
+ */
 #define SEQ_START_TOKEN ((void *)1)
 
 /*
-
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