linux-kernel - Re: FTRACE_WARN_ON((rec->flags & ~FTRACE_FL

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Message-ID: <20130930171201.GA10474@redhat.com>
Date:	Mon, 30 Sep 2013 13:12:01 -0400
From:	Dave Jones <davej@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: FTRACE_WARN_ON((rec->flags & ~FTRACE_FL_MASK) == 0))

On Wed, Aug 28, 2013 at 03:27:45PM -0400, Steven Rostedt wrote:

 > > [ 6619.050768] WARNING: CPU: 1 PID: 16351 at kernel/trace/ftrace.c:1640 __ftrace_hash_rec_update.part.37+0x20a/0x240()
 > > [ 6619.053767] Modules linked in: lec snd_seq_dummy bridge stp fuse tun bnep hidp rfcomm nfnetlink ipt_ULOG scsi_transport_iscsi can_bcm can_raw nfc caif_socket caif af_802154 phonet af_rxrpc bluetooth rfkill can llc2 pppoe pppox ppp_generic slhc irda crc_ccitt rds af_key rose x25 atm netrom appletalk ipx p8023 psnap p8022 llc ax25 xfs libcrc32c snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_page_alloc e1000e ptp snd_timer pcspkr pps_core snd soundcore usb_debug
 > > [ 6619.060523] CPU: 1 PID: 16351 Comm: trinity-child2 Not tainted 3.11.0-rc7+ #31 
 > > [ 6619.062161]  ffffffff81a21901 ffff8802267b9ce0 ffffffff816f9e4f 0000000000000000
 > > [ 6619.063733]  ffff8802267b9d18 ffffffff81052dcd 0000000000000000 0000000000000001
 > > [ 6619.065309]  ffff8802203a3000 0000000000000000 ffff880225e962d0 ffff8802267b9d28
 > > [ 6619.066895] Call Trace:
 > > [ 6619.068437]  [<ffffffff816f9e4f>] dump_stack+0x54/0x74
 > > [ 6619.070046]  [<ffffffff81052dcd>] warn_slowpath_common+0x7d/0xa0
 > > [ 6619.071642]  [<ffffffff81052eaa>] warn_slowpath_null+0x1a/0x20
 > > [ 6619.073224]  [<ffffffff81115d1a>] __ftrace_hash_rec_update.part.37+0x20a/0x240
 > > [ 6619.074817]  [<ffffffff81117e18>] ftrace_shutdown+0xb8/0x160
 > > [ 6619.076399]  [<ffffffff811182a0>] unregister_ftrace_function+0x30/0x50
 > > [ 6619.077983]  [<ffffffff81135e57>] perf_ftrace_event_register+0x87/0x150
 > > [ 6619.079565]  [<ffffffff81135cdc>] perf_trace_destroy+0x2c/0x50
 > > [ 6619.081180]  [<ffffffff8113df49>] tp_perf_event_destroy+0x9/0x10
 > > [ 6619.082742]  [<ffffffff81140527>] free_event+0xa7/0x300
 > > [ 6619.084264]  [<ffffffff81141620>] __perf_event_exit_task+0xe0/0x130
 > > [ 6619.085792]  [<ffffffff8114a491>] perf_event_exit_task+0x1f1/0x230
 > > [ 6619.087329]  [<ffffffff810546dd>] do_exit+0x30d/0xcd0
 > > [ 6619.088860]  [<ffffffff8170cfc0>] ? ftrace_call+0x5/0x2f
 > > [ 6619.090460]  [<ffffffff8105643c>] do_group_exit+0x4c/0xc0
 > > [ 6619.092036]  [<ffffffff810564c4>] SyS_exit_group+0x14/0x20
 > > [ 6619.093614]  [<ffffffff8170d594>] tracesys+0xdd/0xe2
 >
 > The first failure disables function tracing completely, which is one of
 > the causes to return an error, which triggered the warning I added.
 > 
 > I was hoping that it failed for another reason and then that would
 > cause things to break. But you said the hash corruption happened first
 > (the original bug), so that's not the case.
 > 
 > Back to staring at code.

Steve, any further thoughts on this ? I can't do more than a few hours of fuzz-testing
without eventually running into this.

	Dave
 
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