From: Al Viro <viro@ZenIV.linux.org.uk>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: [tracepoint] cargo-culting considered harmful...
Date: Wed, 23 Jan 2013 22:55:24 +0000 [thread overview]
Message-ID: <20130123225523.GY4939@ZenIV.linux.org.uk> (raw)
In samples/tracepoints/tracepoint-probe-sample.c:
/*
* Here the caller only guarantees locking for struct file and struct inode.
* Locking must therefore be done in the probe to use the dentry.
*/
static void probe_subsys_event(void *ignore,
struct inode *inode, struct file *file)
{
path_get(&file->f_path);
dget(file->f_path.dentry);
printk(KERN_INFO "Event is encountered with filename %s\n",
file->f_path.dentry->d_name.name);
dput(file->f_path.dentry);
path_put(&file->f_path);
}
note that
* file->f_path is already pinned down by open(), path_get() does not
provide anything extra.
* file->f_path.dentry is already pinned by open() *and* path_get()
just above that dget().
* ->d_name.name *IS* *NOT* *PROTECTED* by pinning dentry down,
whether it's done once or thrice.
I do realize that it's just an example, but perhaps we should rename that
file to match the contents? The only question is whether it should be
git mv samples/tracepoints/{tracepoint-probe-sample,cargo-cult}.c
or git mv samples cargo-cult...
Al, seriously peeved.
next reply other threads:[~2013-01-23 22:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-23 22:55 Al Viro [this message]
2013-01-23 23:02 ` [tracepoint] cargo-culting considered harmful Steven Rostedt
2013-01-25 14:38 ` Mathieu Desnoyers
2013-01-25 15:27 ` Steven Rostedt
2013-01-25 16:14 ` Mathieu Desnoyers
2013-01-23 23:51 ` Andrew Morton
2013-01-24 1:48 ` Al Viro
2013-01-25 14:49 ` Mathieu Desnoyers
2013-01-25 15:32 ` Al Viro
2013-01-25 17:30 ` Mathieu Desnoyers
2013-02-03 19:16 ` [tip:perf/core] tracing: Remove tracepoint sample code tip-bot for Steven Rostedt
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