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From: Alexander Shishkin <>
To: Song Liu <>
	Alexander Shishkin <>,
	Ingo Molnar <>,
	Peter Zijlstra <>
Subject: Re: [PATCH 2/2] perf/core: fix bad use of igrab in kernel/event/core.c
Date: Thu, 19 Apr 2018 09:17:10 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Apr 17, 2018 at 11:29:07PM -0700, Song Liu wrote:
> As Miklos reported and suggested:
>   This pattern repeats two times in trace_uprobe.c and in
>   kernel/events/core.c as well:
>       ret = kern_path(filename, LOOKUP_FOLLOW, &path);
>       if (ret)
>           goto fail_address_parse;
>       inode = igrab(d_inode(path.dentry));
>       path_put(&path);
>   And it's wrong.  You can only hold a reference to the inode if you
>   have an active ref to the superblock as well (which is normally
>   through path.mnt) or holding s_umount.

Oops. I must have snatched it from the uprobe code without thinking.

>   This way unmounting the containing filesystem while the tracepoint is
>   active will give you the "VFS: Busy inodes after unmount..." message
>   and a crash when the inode is finally put.
>   Solution: store path instead of inode.
> This patch fixes the issue in kernel/event/core.c.
> NOTE: Based on my understanding, perf_addr_filter only supports intel_pt.

Coresight too, but that's probably even further away from what you have.

> However, my test system doesn't support address filtering (or I made a
> mistake?). Therefore, I have NOT tested this patch.

Check /sys/devices/intel_pt/caps/num_address_ranges, if it's non-zero,
it's supported.

> Could someone please help test it?


Reviewed-and-tested-by: Alexander Shishkin <>

The subject line needs a little love to be more like other perf commits, but
other than that, looks good.


  reply	other threads:[~2018-04-19  6:17 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18  6:29 [PATCH 1/2] tracing: fix bad use of igrab in trace_uprobe.c Song Liu
2018-04-18  6:29 ` [PATCH 2/2] perf/core: fix bad use of igrab in kernel/event/core.c Song Liu
2018-04-19  6:17   ` Alexander Shishkin [this message]
2018-05-22 21:56     ` Song Liu
2018-05-23 13:11       ` Peter Zijlstra
2018-05-25  9:49   ` [tip:perf/core] perf/core: Fix bad use of igrab() tip-bot for Song Liu
2018-04-18 14:03 ` [PATCH 1/2] tracing: fix bad use of igrab in trace_uprobe.c Miklos Szeredi
2018-04-18 14:25   ` Steven Rostedt
2018-04-18 14:40     ` Miklos Szeredi
2018-04-18 15:19       ` Steven Rostedt
2018-04-18 16:15     ` Song Liu
2018-04-18 16:08   ` Song Liu
2018-04-18 16:25     ` Steven Rostedt

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