On 2/02/2016 5:52 p.m., Arnaldo Carvalho de Melo wrote:
Em Tue, Feb 02, 2016 at 12:24:19PM +0200, Adrian Hunter escreveu:
This patch does not fix the problem because the thread__zput() will still
segfault later if the error path is not taken.
Sorry, I didn't look closely at this patch because I was not expecting it
to be taken because of the fix I had already sent:
http://marc.info/?l=linux-kernel&m=145431692623940
However if you want to keep the struct thread rbtree / list union, the
simple fix would be to reinstate the list initialization in this particular
case i.e.:
So, can I go with the following patch+description+authorship?
Fine by me. Thank you!
From 3a4acda1ecbd290973de08250d7dcdfaf5b2fe0f Mon Sep 17 00:00:00 2001
From: Adrian Hunter <adrian.hun...@intel.com>
Date: Mon, 1 Feb 2016 03:21:04 +0000
Subject: [PATCH 1/1] perf tools: Fix thread lifetime related segfaut in intel_pt
intel_pt_process_auxtrace_info() creates a pt->unknown_thread thread
that eventually needs to be freed by the last thread__put() on it, when
its refcount hits zero, which may happen in
intel_pt_process_auxtrace_info() error handling path and triggers the
following segfault, which would happen as well at intel_pt_free, when
tools using this intel_pt codebase frees up resources:
# perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
0 a anaconda-ks.cfg bin perf.data perf.data.old
perf-f23-bringup.todo
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.217 MB perf.data ]
#
# perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
Samples for 'instructions:u' event do not have IREGS attribute set. Cannot
print 'iregs' field.
intel_pt_synth_events: failed to synthesize 'instructions' event type
Segmentation fault (core dumped)
#
The problem is: there's a union in 'struct thread' combines a list_head
and a rb_node. The standard life cycle of a thread is: init rb_node in
the constructor, insert it into machine->threads rbtree using rb_node,
move it to machine->dead_threads using list_head, clean in the last
thread__put: list_del_init(&thread->node).
In the above command, it clean a thread before adding it into list,
causes the above segfault.
Since pt->unknown_thread will never live in an rbtree, initialize its
list node so that when list_del_init() is done on it we don't segfault.
After this patch:
# perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
Samples for 'instructions:u' event do not have IREGS attribute set. Cannot
print 'iregs' field.
intel_pt_synth_events: failed to synthesize 'instructions' event type
0x248 [0x88]: failed to process type: 70
#
Reported-by: Tong Zhang <zt...@vt.edu>
Reported-by: Wang Nan <wangn...@huawei.com>
Signed-off-by: Adrian Hunter <adrian.hun...@intel.com>
Tested-by: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Link:
http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangn...@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
---
tools/perf/util/intel-pt.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 81a2eb77ba7f..05d815851be1 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -2068,6 +2068,15 @@ int intel_pt_process_auxtrace_info(union perf_event
*event,
err = -ENOMEM;
goto err_free_queues;
}
+
+ /*
+ * Since this thread will not be kept in any rbtree not in a
+ * list, initialize its list node so that at thread__put() the
+ * current thread lifetime assuption is kept and we don't segfault
+ * at list_del_init().
+ */
+ INIT_LIST_HEAD(&pt->unknown_thread->node);
+
err = thread__set_comm(pt->unknown_thread, "unknown", 0);
if (err)
goto err_delete_thread;
