The stat entries can be freed when the stat file is being read.
The worse is, the ptr can be freed immediately after it's returned
from workqueue_stat_start/next().

Add a refcnt to struct cpu_workqueue_stats to avoid use-after-free.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A51B16F.6010608@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The blankline between each cpu's workqueue stat is not necessary, because
the cpu number is enough to part them by eye.
Old style also caused a blankline below headline, and made code complex
by using lock, disableirq and get cpu var.

Old style:
 # CPU  INSERTED  EXECUTED   NAME
 # |      |         |          |

   0   8644       8644       events/0
   0      0          0       cpuset
   ...
   0      1          1       kdmflush

   1  35365      35365       events/1
   ...

New style:
 # CPU  INSERTED  EXECUTED   NAME
 # |      |         |          |

   0   8644       8644       events/0
   0      0          0       cpuset
   ...
   0      1          1       kdmflush
   1  35365      35365       events/1
   ...

[ Impact: provide more readable code ]

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

cpu_workqueue_stats->first_entry is useless because we can retrieve the
header of a cpu workqueue using:
if (&cpu_workqueue_stats->list == workqueue_cpu_stat(cpu)->list.next)

[ Impact: cleanup ]

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

No need to use list_for_each_entry_safe() in iteration without deleting
any node, we can use list_for_each_entry() instead.

[ Impact: cleanup ]

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

v3: zhaolei@cn.fujitsu.com: Change TRACE_EVENT definition to new format
    introduced by Steven Rostedt: consolidate trace and trace_event headers
v2: kosaki@jp.fujitsu.com: print the function names instead of addr, and zap
    the work addr
v1: zhaolei@cn.fujitsu.com: Make workqueue tracepoints use TRACE_EVENT macro

TRACE_EVENT is a more generic way to define tracepoints.
Doing so adds these new capabilities to the tracepoints:

  - zero-copy and per-cpu splice() tracing
  - binary tracing without printf overhead
  - structured logging records exposed under /debug/tracing/events
  - trace events embedded in function tracer output and other plugins
  - user-defined, per tracepoint filter expressions

Then, this patch converts DEFINE_TRACE to TRACE_EVENT in workqueue related
tracepoints.

[ Impact: expand workqueue tracer to events tracing ]

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Merge reason: update to upstream tracing facilities

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Empty lines separate cpus stat. After previous
fix(trace_stat: keep original order) applied, the empty lines
are displayed at incorrect position.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49C9F266.2060706@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Currently, if a trace_stat user wants a handle to some private data,
the trace_stat infrastructure does not supply a way to do that.

This patch passes the trace_stat structure to the start function of
the trace_stat code.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

commit c3ffc7a40b7e94b094efe1c8ab4e24370a782b65
"Don't use tracing_record_cmdline() in workqueue tracer"
has a race window.

find_task_by_vpid() requires task_list_lock().

LKML-Reference: <20090313090042.43CD.A69D9226@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>