From: Wang Nan <wangn...@huawei.com> In error processing path of intel_pt_process_auxtrace_info() it calls thread__zput() to clean and free pt->unknown_thread which is created by thread__new(). However, when error raise, a segfault happen:
# 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 during creating, inserted into machine->threads rbtree uses rb_node, move to machine->dead_threads using list_head, clean by thread__put: list_del_init(&thread->node). In the above command, it clean a thread before adding it into list, causes the above segfault. This patch gives a fake list_head and link the thread into it before calling thread__zput(), get rid of the 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> Signed-off-by: Wang Nan <wangn...@huawei.com> Tested-by: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Adrian Hunter <adrian.hun...@intel.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 | 4 ++++ 1 file changed, 4 insertions(+) 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(); -- 2.5.0
