| Message ID | 1454346792-24419-3-git-send-email-acme@kernel.org |
|---|---|
| State | New |
| Headers | show |
On 2016/2/2 23:52, 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? I didn't really understand the lifecycle of unknown_thread, and though it would go to an rbtree in normal path. I think the patch you posted is good. Thank you. > From 3a4acda1ecbd290973de08250d7dcdfaf5b2fe0f Mon Sep 17 00:00:00 2001 > From: Adrian Hunter <adrian.hunter@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 <ztong@vt.edu> > Reported-by: Wang Nan <wangnan0@huawei.com> > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> > Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Link: http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangnan0@huawei.com > Signed-off-by: Arnaldo Carvalho de Melo <acme@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;
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c index 81a2eb77ba7f..e2add6376fec 100644 --- a/tools/perf/util/intel-pt.c +++ b/tools/perf/util/intel-pt.c @@ -2013,6 +2013,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, struct auxtrace_info_event *auxtrace_info = &event->auxtrace_info; size_t min_sz = sizeof(u64) * INTEL_PT_PER_CPU_MMAPS; struct intel_pt *pt; + struct list_head dead_thread; int err; if (auxtrace_info->header.size < sizeof(struct auxtrace_info_event) + @@ -2153,6 +2154,9 @@ int intel_pt_process_auxtrace_info(union perf_event *event, return 0; err_delete_thread: + RB_CLEAR_NODE(&pt->unknown_thread->rb_node); + INIT_LIST_HEAD(&dead_thread); + list_add(&pt->unknown_thread->node, &dead_thread); thread__zput(pt->unknown_thread); err_free_queues: intel_pt_log_disable();