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[GIT PULL 0/2] perf/urgent fixes

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  [GIT PULL 0/2] perf/urgent fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-01 18:20 +0100
    [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info() Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-01 18:20 +0100
      Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() Adrian Hunter <adrian.hunter@intel.com> - 2016-02-02 11:30 +0100
        Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-02 15:10 +0100
        Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-02 17:00 +0100
          Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-02 21:40 +0100
          Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() "Wangnan (F)" <wangnan0@huawei.com> - 2016-02-03 03:10 +0100
          Re: [PATCH 2/2] perf tools: Fix fault in error patch of  intel_pt_process_auxtrace_info() Adrian Hunter <adrian.hunter@intel.com> - 2016-02-03 08:10 +0100

#1323331 — [GIT PULL 0/2] perf/urgent fixes

See http://www.infradead.org/rpr.html

Hi Ingo,

	Please consider pulling,

- Arnaldo

The following changes since commit 28fb8a5b6e233fc384fb27f9f91f811b40ba9cf8:

  Merge tag 'perf-urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent (2016-01-30 09:15:49 +0100)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tags/perf-urgent-for-mingo

for you to fetch changes up to d3a37ea00a9fbc0f4fa91647c9ae66c038ba65e3:

  perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info() (2016-02-01 12:03:35 -0300)

----------------------------------------------------------------
perf/urgent fixes:

- tracepoint_error() can receive e=NULL, robustify it, fixes a problem noticed
  with a very specific combination: Machine with Intel PT (e.g. Broadwell),
  kernel with no perf_event_attr.context_switch feature (e.g. 4.2) and unreadable
  tracefs (for instance !root users), making the fallback from
  perf_event_attr.context_switch to the sched:sched_switch tracepoint to fail
  reading its info from tracefs, fix it. (Adrian Hunter)

- Fix fault in error path of intel_pt_process_auxtrace_info(), obeying
  the existing 'struct thread' lifetime cycle checking expectations, noticed
  for instance, when processing perf.data files with Intel PT data using
  'perf script' (Wang Nan)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

----------------------------------------------------------------
Adrian Hunter (1):
      perf tools: tracepoint_error() can receive e=NULL, robustify it

Wang Nan (1):
      perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

 tools/perf/util/intel-pt.c     | 4 ++++
 tools/perf/util/parse-events.c | 3 +++
 2 files changed, 7 insertions(+)

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#1323334 — [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

From: Wang Nan <wangnan0@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 <ztong@vt.edu>
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.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 | 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

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#1323947 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

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.:


diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 81a2eb7..18245b8 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -2068,6 +2068,7 @@ int intel_pt_process_auxtrace_info(union perf_event
                err = -ENOMEM;
                goto err_free_queues;
        }
+       INIT_LIST_HEAD(&pt->unknown_thread->node);
        err = thread__set_comm(pt->unknown_thread, "unknown", 0);
        if (err)
                goto err_delete_thread;



On 01/02/16 19:13, Arnaldo Carvalho de Melo wrote:
> From: Wang Nan <wangnan0@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 <ztong@vt.edu>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Adrian Hunter <adrian.hunter@intel.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 | 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();
> 

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#1324111 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

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.:

Right, so it keeps the existing thread lifetime assumptions both in the
error path, as Wang did, and in the normal pt->unknown_thread end of
life at intel_pt_free(), I'm replacing the patch...

- Arnaldo
 
> 
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index 81a2eb7..18245b8 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -2068,6 +2068,7 @@ int intel_pt_process_auxtrace_info(union perf_event
>                 err = -ENOMEM;
>                 goto err_free_queues;
>         }
> +       INIT_LIST_HEAD(&pt->unknown_thread->node);
>         err = thread__set_comm(pt->unknown_thread, "unknown", 0);
>         if (err)
>                 goto err_delete_thread;
> 
> 
> 
> On 01/02/16 19:13, Arnaldo Carvalho de Melo wrote:
> > From: Wang Nan <wangnan0@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 <ztong@vt.edu>
> > Signed-off-by: Wang Nan <wangnan0@huawei.com>
> > Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Cc: Adrian Hunter <adrian.hunter@intel.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 | 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();
> > 

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#1324223 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

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?

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;
-- 
2.5.0

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#1324609 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

Em Tue, Feb 02, 2016 at 12:52:25PM -0300, Arnaldo Carvalho de Melo escreveu:
> 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?

BTW, I just noticed it while testing some unrelated patch (Jiri's hpp
hists stuff) that with a perf.data file with intel pt data, I get this
at the end of a TUI session, i.e. the segfault at tool exit:


Available samples
0 intel_pt/tsc=1,noretcomp=1/u                                                                                                                                              ◆
29 sched:sched_switch                                                                                                                                                       ▒
0 dummy:u                                                                                                                                                                   ▒
6 instructions:u                                                                                                                                                            ▒
0 transactions                                                                                                                                                              ▒
                                                                                                                                                                            Program received signal SIGSEGV, Segmentation fault.                                                                                                                         ▒
                                                   0x00000000004ec5c5 in __write_once_size (size=8, res=0x7fffffffc2e0, p=0x0) at /home/acme/git/linux/tools/include/linux/compiler.h:82                                                                                                                                                                 ▒
82              case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;                                                                                      ▒
Missing separate debuginfos, use: dnf debuginfo-install audit-libs-2.4.5-1.fc23.x86_64 bzip2-libs-1.0.6-19.fc23.x86_64 elfutils-libelf-0.165-2.fc23.x86_64 elfutils-libs-0.165-2.fc23.x86_64 libunwind-1.1-10.fc23.x86_64 nss-softokn-freebl-3.21.0-1.1.fc23.x86_64 numactl-libs-2.0.10-3.fc23.x86_64 perl-libs-5.22.1-350.fc23.x86_64 python-libs-2.7.10-8.fc23.x86_64 slang-2.3.0-4.fc23.x86_64 xz-libs-5.2.1-3.fc23.x86_64 zlib-1.2.8-9.fc23.x86_64                                                                                ▒
(gdb) bt                                                                                                                                                                    ▒
#0  0x00000000004ec5c5 in __write_once_size (size=8, res=0x7fffffffc2e0, p=0x0) at /home/acme/git/linux/tools/include/linux/compiler.h:82                                   ▒
#1  __list_del (prev=0x0, next=0x1a2e970) at /home/acme/git/linux/tools/include/linux/list.h:89                                                                             ▒
#2  0x00000000004ec631 in __list_del_entry (entry=0x1a2e970) at /home/acme/git/linux/tools/include/linux/list.h:101                                                         ▒
#3  0x00000000004ec6d2 in list_del_init (entry=0x1a2e970) at /home/acme/git/linux/tools/include/linux/list.h:144                                                            ▒
#4  0x00000000004ecd2a in thread__put (thread=0x1a2e970) at util/thread.c:104                                                                                               ▒
#5  0x000000000052de51 in intel_pt_free (session=0x19a3b90) at util/intel-pt.c:1747                                                                                         ▒
#6  0x00000000004e4e3d in auxtrace__free (session=0x19a3b90) at util/auxtrace.h:513                                                                                         ▒
#7  0x00000000004e5603 in perf_session__delete (session=0x19a3b90) at util/session.c:181                                                                                    ▒
#8  0x00000000004363f3 in cmd_report (argc=0, argv=0x7fffffffdeb0, prefix=0x0) at builtin-report.c:984                                                                      ▒
#9  0x000000000049bea3 in run_builtin (p=0x8fa2c0 <commands+192>, argc=1, argv=0x7fffffffdeb0) at perf.c:390                                                                ▒
#10 0x000000000049c10b in handle_internal_command (argc=1, argv=0x7fffffffdeb0) at perf.c:451                                                                               ▒
#11 0x000000000049c259 in run_argv (argcp=0x7fffffffdd0c, argv=0x7fffffffdd00) at perf.c:495                                                                                ▒
#12 0x000000000049c5eb in main (argc=1, argv=0x7fffffffdeb0) at perf.c:618                                                                                                  ▒
(gdb) 
 
> 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;
> -- 
> 2.5.0
> 

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#1324825 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

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;

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#1324979 — Re: [PATCH 2/2] perf tools: Fix fault in error patch of intel_pt_process_auxtrace_info()

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.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;
>

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