----- On Mar 20, 2018, at 5:42 PM, Mathieu Desnoyers
<mathieu.desnoy...@efficios.com> wrote:
> ----- On Mar 20, 2018, at 4:58 PM, Mathieu Desnoyers
> <mathieu.desnoy...@efficios.com> wrote:
>> ----- On Mar 20, 2018, at 12:07 PM, Mathieu Desnoyers
>> <mathieu.desnoy...@efficios.com> wrote:
>>> ----- On Mar 19, 2018, at 4:21 PM, Shehab Elsayed <shehaby...@gmail.com>
>>> wrote:
>>>> I did "echo "-1" > /proc/sys/kernel/perf_event_paranoid " and made sure the
>>>> value was actually written by "cat /proc/sys/kernel/perf_event_paranoid"
>>>> It executed normally 2 times but then got the same error.
>>> Can you provide the output when reproducing the issue with the
>>> LTTNG_UST_DEBUG=1 environment variable set when starting
>>> your test program ?
>> I just noticed something that might explain what goes wrong here:
>> lttng-context-perf-counters.c: add_thread_field() grabs the ust_lock().
>> Pthread
>> mutex
>> in your case is instrumented with the pthread wrapper. This
>> "add_thread_field"
>> is invoked
>> the first time the perf counter is hit by each given thread. When this
>> happens,
>> the
>> instrumented pthread mutex will try to call into the instrumentation
>> tracepoint
>> again,
>> which will call add_thread_field() (again), and so on until we reach the
>> libringbuffer
>> "lib_ring_buffer_nesting" threshold of 4 calls deep.
>> I suspect this situation where we recursively call add_thread_field is
>> unexpected,
>> which may trigger your double-free here.
>> Will investigate more.
> Can you try with the attached patch applied ?
Here is an updated v2 of the patch which tests the notrace tls counter sooner
(before evaluating
filter). Please let me know how it goes.
Thanks,
Mathieu
> Thanks,
> Mathieu
>> Thanks,
>> Mathieu
>>> Thanks,
>>> Mathieu
>>>> Shehab Y. Elsayed, MSc.
>>>> PhD Student
>>>> The Edwards S. Rogers Sr. Dept. of Electrical and Computer Engineering
>>>> University of Toronto
>>>> E-mail: [ https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11#
>>>> |
>>>> shehaby...@gmail.com ]
>>>> On Mon, Mar 19, 2018 at 4:01 PM, Mathieu Desnoyers < [
>>>> mailto:mathieu.desnoy...@efficios.com | mathieu.desnoy...@efficios.com ] >
>>>> wrote:
>>>>> ----- On Mar 19, 2018, at 3:53 PM, Shehab Elsayed < [
>>>>> mailto:shehaby...@gmail.com | shehaby...@gmail.com ] > wrote:
>>>>>> cat /proc/sys/kernel/perf_event_paranoid ---> returns 1
>>>>>> I run the program as a normal user
>>>>>> The glibc version I get by running "ldd --version" is 2.17
>>>>> Can you reproduce the issue after you do this as root ?
>>>>> echo "-1" > /proc/sys/kernel/perf_event_paranoid
>>>>> Based on this documentation of the Linux kernel:
>>>>> Documentation/sysctl/kernel.txt:
>>>>> perf_event_paranoid:
>>>>> Controls use of the performance events system by unprivileged
>>>>> users (without CAP_SYS_ADMIN). The default value is 2.
>>>>> -1: Allow use of (almost) all events by all users
>>>>> Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
>>>>> >=0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
>>>>> Disallow raw tracepoint access by users without CAP_SYS_ADMIN
>>>>> >=1: Disallow CPU event access by users without CAP_SYS_ADMIN
>>>>> >=2: Disallow kernel profiling by users without CAP_SYS_ADMIN
>>>>> Thanks,
>>>>> Mathieu
>>>>>> Shehab Y. Elsayed, MSc.
>>>>>> PhD Student
>>>>>> The Edwards S. Rogers Sr. Dept. of Electrical and Computer Engineering
>>>>>> University of Toronto
>>>>>> E-mail: [
>>>>>> https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11# |
>>>>>> shehaby...@gmail.com ]
>>>>>> On Mon, Mar 19, 2018 at 3:31 PM, Mathieu Desnoyers < [
>>>>>> mailto:mathieu.desnoy...@efficios.com | mathieu.desnoy...@efficios.com ]
>>>>>> >
>>>>>> wrote:
>>>>>>> ---- On Mar 19, 2018, at 3:26 PM, Mathieu Desnoyers < [
>>>>>>> mailto:mathieu.desnoy...@efficios.com | mathieu.desnoy...@efficios.com
>>>>>>> ] >
>>>>>>> wrote:
>>>>>>>> ----- On Mar 19, 2018, at 2:26 PM, Shehab Elsayed < [
>>>>>>>> mailto:shehaby...@gmail.com | shehaby...@gmail.com ] > wrote:
>>>>>>>>> Yes, I tried with only one of those contexts and I still ran into the
>>>>>>>>> same
>>>>>>>>> problem.
>>>>>>>> What is the setting returned by
>>>>>>>> cat /proc/sys/kernel/perf_event_paranoid
>>>>>>>> on your system ? And do you run your test program as root or normal
>>>>>>>> user ?
>>>>>>>> Please CC the mailing list on your reply.
>>>>>>> I will also need to know what glibc version you have on your system.
>>>>>>> Thanks,
>>>>>>> Mathieu
>>>>>>>> Thanks,
>>>>>>>> Mathieu
>>>>>>>>> Shehab Y. Elsayed, MSc.
>>>>>>>>> PhD Student
>>>>>>>>> The Edwards S. Rogers Sr. Dept. of Electrical and Computer Engineering
>>>>>>>>> University of Toronto
>>>>>>>>> E-mail: [
>>>>>>>>> https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11# |
>>>>>>>>> shehaby...@gmail.com ]
>>>>>>>>> On Mon, Mar 19, 2018 at 2:24 PM, Mathieu Desnoyers < [
>>>>>>>>> mailto:mathieu.desnoy...@efficios.com |
>>>>>>>>> mathieu.desnoy...@efficios.com ] >
>>>>>>>>> wrote:
>>>>>>>>>> ----- On Mar 19, 2018, at 12:36 PM, Shehab Elsayed < [
>>>>>>>>>> mailto:shehaby...@gmail.com | shehaby...@gmail.com ] > wrote:
>>>>>>>>>>> Hi Mathieu,
>>>>>>>>>>> Thank you very much for your reply.
>>>>>>>>>>> I manually built lttng-ust from source (commit #:
>>>>>>>>>>> 8a208943e21700211beee3ea64180a5a534c7d2a).
>>>>>>>>>>> This is how I set up the tracing session:
>>>>>>>>>>> 1- lttng create lu_ncb_8_native -o {path}
>>>>>>>>>>> 2- lttng enable-event --userspace
>>>>>>>>>>> lttng_ust_pthread:pthread_mutex_lock_req
>>>>>>>>>>> lttng enable-event --userspace
>>>>>>>>>>> lttng_ust_pthread:pthread_mutex_lock_acq
>>>>>>>>>>> lttng enable-event --userspace
>>>>>>>>>>> lttng_ust_pthread:pthread_mutex_lock_trylock
>>>>>>>>>>> lttng enable-event --userspace
>>>>>>>>>>> lttng_ust_pthread:pthread_mutex_lock_unlock
>>>>>>>>>>> 3- lttng add-context -u -t procname
>>>>>>>>>>> lttng add-context -u -t vpid
>>>>>>>>>>> lttng add-context -u -t pthread_id
>>>>>>>>>>> lttng add-context -u -t vtid
>>>>>>>>>>> lttng add-context -u -t ip
>>>>>>>>>>> lttng add-context -u -t perf:thread:cpu-cycles
>>>>>>>>>>> lttng add-context -u -t perf:thread:cycles
>>>>>>>>>>> lttng add-context -u -t perf:thread:instructions
>>>>>>>>>>> 4- lttng start
>>>>>>>>>>> 5- LD_PRELOAD=/usr/local/lib/liblttng-ust-pthread-wrapper.so
>>>>>>>>>>> ./lu_ncb -p8 -n8096
>>>>>>>>>>> -b32
>>>>>>>>>>> 6- lttng stop
>>>>>>>>>>> 7- lttng destroy
>>>>>>>>>> Can you reproduce if you remove the following contexts ?
>>>>>>>>>> lttng add-context -u -t perf:thread:cpu-cycles
>>>>>>>>>> lttng add-context -u -t perf:thread:cycles
>>>>>>>>>> lttng add-context -u -t perf:thread:instructions
>>>>>>>>>> And if you only keep a single of those contexts ?
>>>>>>>>>> Thanks,
>>>>>>>>>> Mathieu
>>>>>>>>>>> Shehab Y. Elsayed, MSc.
>>>>>>>>>>> PhD Student
>>>>>>>>>>> The Edwards S. Rogers Sr. Dept. of Electrical and Computer
>>>>>>>>>>> Engineering
>>>>>>>>>>> University of Toronto
>>>>>>>>>>> E-mail: [
>>>>>>>>>>> https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11# |
>>>>>>>>>>> shehaby...@gmail.com ]
>>>>>>>>>>> On Mon, Mar 19, 2018 at 12:21 PM, Mathieu Desnoyers < [
>>>>>>>>>>> mailto:mathieu.desnoy...@efficios.com |
>>>>>>>>>>> mathieu.desnoy...@efficios.com ] >
>>>>>>>>>>> wrote:
>>>>>>>>>>>> ----- On Mar 16, 2018, at 5:37 PM, Shehab Elsayed < [
>>>>>>>>>>>> mailto:shehaby...@gmail.com | shehaby...@gmail.com ] > wrote:
>>>>>>>>>>>>> Hello All,
>>>>>>>>>>>>> I am trying to instrument a pthread application using the
>>>>>>>>>>>>> provided pthread
>>>>>>>>>>>>> wrapper, but I sometimes run into a "Double free or corruption
>>>>>>>>>>>>> error ( fasttop
>>>>>>>>>>>>> )" error.
>>>>>>>>>>>> Please provide more information about the version of lttng-ust you
>>>>>>>>>>>> are using,
>>>>>>>>>>>> and how you setup
>>>>>>>>>>>> your tracing session.
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>> Mathieu
>>>>>>>>>>>>> Here is a description of what I have tried and noticed:
>>>>>>>>>>>>> 1- The problem isn't consistent. It sometimes happen and
>>>>>>>>>>>>> sometimes works as
>>>>>>>>>>>>> expected.
>>>>>>>>>>>>> 2- From my experiments, the problem happens (more frequently at
>>>>>>>>>>>>> least) when
>>>>>>>>>>>>> adding performance counter contexts (I tried cycles, cpu _cycles
>>>>>>>>>>>>> and
>>>>>>>>>>>>> instructions).
>>>>>>>>>>>>> 3- I am testing using lu _ ncb from splash3 benchmark suite after
>>>>>>>>>>>>> setting LD _
>>>>>>>>>>>>> PRELOAD to use the pthread wrapper as described in the LTTng
>>>>>>>>>>>>> documents.
>>>>>>>>>>>>> 4- Here is the backtrace printed after exiting:
>>>>>>>>>>>>> ======= Backtrace : =========
>>>>>>>>>>>>> /lib64/ libc .so.6([Thread 0x7ffff5611700 ( LWP 97229) exited]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng
>>>>>>>>>>>>> _destroy_context+0x35)[0x7ffff7471575]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng
>>>>>>>>>>>>> _session_destroy+0x21c)[0x7ffff747363c]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0(+0x1e906)[0x7ffff746d906]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng _ ust _ objd _ unref
>>>>>>>>>>>>> +0x9f)[0x7ffff746dccf]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng _ ust _ objd _ unref
>>>>>>>>>>>>> +0x9f)[0x7ffff746dccf]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng _ ust _ objd _ unref
>>>>>>>>>>>>> +0x9f)[0x7ffff746dccf]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng _ ust _ abi
>>>>>>>>>>>>> _exit+0x68)[0x7ffff746ead8]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0(+0x191d3)[0x7ffff74681d3]
>>>>>>>>>>>>> / usr /local/lib/ liblttng - ust .so.0( lttng _ ust
>>>>>>>>>>>>> _exit+0x67)[0x7ffff745ed57]
>>>>>>>>>>>>> /lib64/ ld - linux -x86-64.so.2(+0xf85a)[0x7ffff7dec85a]
>>>>>>>>>>>>> /lib64/ libc .so.6(+0x38a49)[0x7ffff6ca6a49]
>>>>>>>>>>>>> /lib64/ libc .so.6(+0x38a95)[0x7ffff6ca6a95]
>>>>>>>>>>>>> / aenao -99/elsayed9/ LTTng /data/scripts/ tmp / lu _ ncb
>>>>>>>>>>>>> [0x401b51]
>>>>>>>>>>>>> /lib64/ libc .so.6(__ libc _start_main+0xf5)[0x7ffff6c8fb35]
>>>>>>>>>>>>> / aenao -99/elsayed9/ LTTng /data/scripts/ tmp / lu _ ncb
>>>>>>>>>>>>> [0x401c44]
>>>>>>>>>>>>> 5- Also, this is a backtrace I obtained from gdb :
>>>>>>>>>>>>> #0 0x00007ffff6eac1d7 in raise () from /lib64/ libc .so.6
>>>>>>>>>>>>> #1 0x00007ffff6ead8c8 in abort () from /lib64/ libc .so.6
>>>>>>>>>>>>> #2 0x00007ffff6eebf07 in __ libc _message () from /lib64/ libc
>>>>>>>>>>>>> .so.6
>>>>>>>>>>>>> #3 0x00007ffff6ef3503 in _int_free () from /lib64/ libc .so.6
>>>>>>>>>>>>> #4 0x00007ffff768ad25 in lttng _destroy_ perf _counter_field (
>>>>>>>>>>>>> field=<optimized out>) at lttng -context- perf -counters.c:418
>>>>>>>>>>>>> #5 0x00007ffff767a575 in lttng _destroy_context (
>>>>>>>>>>>>> ctx =0x7ffff0011090) at lttng -context.c:278
>>>>>>>>>>>>> #6 0x00007ffff767c63c in _ lttng _channel_ unmap (
>>>>>>>>>>>>> lttng _ chan =0x7ffff0010f40) at lttng -events.c:172
>>>>>>>>>>>>> #7 lttng _session_destroy (session=0x7ffff0000900)
>>>>>>>>>>>>> at lttng -events.c:247
>>>>>>>>>>>>> #8 0x00007ffff7676906 in lttng _release_session (
>>>>>>>>>>>>> objd =<optimized out>) at lttng - ust - abi .c:601
>>>>>>>>>>>>> #9 0x00007ffff7676ccf in lttng _ ust _ objd _ unref (id=1,
>>>>>>>>>>>>> is_owner=<optimized out>) at lttng - ust - abi .c:216
>>>>>>>>>>>>> #10 0x00007ffff7676ccf in lttng _ ust _ objd _ unref (id=2,
>>>>>>>>>>>>> is_owner=<optimized out>) at lttng - ust - abi .c:216
>>>>>>>>>>>>> #11 0x00007ffff7676ccf in lttng _ ust _ objd _ unref
>>>>>>>>>>>>> (id=id@entry=18,
>>>>>>>>>>>>> is_owner=is_owner@entry=1) at lttng - ust - abi .c:216
>>>>>>>>>>>>> #12 0x00007ffff7677ad8 in objd _table_destroy ()
>>>>>>>>>>>>> at lttng - ust - abi .c:235
>>>>>>>>>>>>> #13 lttng _ ust _ abi _exit () at lttng - ust - abi .c:1002
>>>>>>>>>>>>> #14 0x00007ffff76711d3 in lttng _ ust _cleanup (exiting=1)
>>>>>>>>>>>>> at lttng - ust -comm.c:1807
>>>>>>>>>>>>> #15 0x00007ffff7667d57 in lttng _ ust _exit ()
>>>>>>>>>>>>> at lttng - ust -comm.c:1874
>>>>>>>>>>>>> #16 0x00007ffff7dec85a in _ dl _ fini ()
>>>>>>>>>>>>> from /lib64/ ld - linux -x86-64.so.2
>>>>>>>>>>>>> #17 0x00007ffff6eafa49 in __run_exit_handlers ()
>>>>>>>>>>>>> from /lib64/ libc .so.6
>>>>>>>>>>>>> #18 0x00007ffff6eafa95 in exit () from /lib64/ libc .so.6
>>>>>>>>>>>>> #19 0x0000000000401b51 in main ( argc =<optimized out>,
>>>>>>>>>>>>> argv =<optimized out>) at lu .c:368
>>>>>>>>>>>>> Any ideas, why this happens and how to fix it?
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>> Shehab
>>>>>>>>>>>>> _______________________________________________
>>>>>>>>>>>>> lttng-dev mailing list
>>>>>>>>>>>>> [ mailto:lttng-dev@lists.lttng.org | lttng-dev@lists.lttng.org ]
>>>>>>>>>>>>> [ https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev |
>>>>>>>>>>>>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ]
>>>>>>>>>>>> --
>>>>>>>>>>>> Mathieu Desnoyers
>>>>>>>>>>>> EfficiOS Inc.
>>>>>>>>>>>> [ http://www.efficios.com/ | http://www.efficios.com ]
>>>>>>>>>> --
>>>>>>>>>> Mathieu Desnoyers
>>>>>>>>>> EfficiOS Inc.
>>>>>>>>>> [ http://www.efficios.com/ | http://www.efficios.com ]
>>>>>>>> --
>>>>>>>> Mathieu Desnoyers
>>>>>>>> EfficiOS Inc.
>>>>>>>> [ http://www.efficios.com/ | http://www.efficios.com ]
>>>>>>> --
>>>>>>> Mathieu Desnoyers
>>>>>>> EfficiOS Inc.
>>>>>>> [ http://www.efficios.com/ | http://www.efficios.com ]
>>>>> --
>>>>> Mathieu Desnoyers
>>>>> EfficiOS Inc.
>>>>> [ http://www.efficios.com/ | http://www.efficios.com ]
>>> --
>>> Mathieu Desnoyers
>>> EfficiOS Inc.
>>> http://www.efficios.com
>> --
>> Mathieu Desnoyers
>> EfficiOS Inc.
>> http://www.efficios.com
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
From 8671c6ae839615c0779041abada4703680fbc003 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Date: Tue, 20 Mar 2018 17:32:36 -0400
Subject: [RFC PATCH v2] Fix: perf event mutex with pthread wrapper
We do not want to recurse in the pthread mutex instrumentation when
setting up the perf counters for a given thread.
Introduce a "notrace" per-thread counter to inhibit tracing for the
current thread.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
---
include/lttng/ust-events.h | 6 ++++++
include/lttng/ust-tracepoint-event.h | 7 ++-----
liblttng-ust/lttng-context-perf-counters.c | 2 ++
liblttng-ust/lttng-events.c | 14 ++++++++++++++
liblttng-ust/lttng-tracer-core.h | 3 +++
liblttng-ust/lttng-ust-comm.c | 23 +++++++++++++++++++++++
6 files changed, 50 insertions(+), 5 deletions(-)
diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 86733503..f8c130f9 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -738,6 +738,12 @@ struct lttng_enum *lttng_ust_enum_get_from_desc(struct lttng_session *session,
void lttng_ust_dl_update(void *ip);
void lttng_ust_fixup_fd_tracker_tls(void);
+void lttng_ust_begin_notrace(void);
+void lttng_ust_end_notrace(void);
+
+int lttng_ust_do_trace(struct lttng_session *session,
+ struct lttng_channel *chan, struct lttng_event *event);
+
/* For backward compatibility. Leave those exported symbols in place. */
extern struct lttng_ctx *lttng_static_ctx;
void lttng_context_init(void);
diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index ec292d24..0bc002f7 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -766,11 +766,8 @@ void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args)) \
(void) __dynamic_len_idx; /* don't warn if unused */ \
if (!_TP_SESSION_CHECK(session, __chan->session)) \
return; \
- if (caa_unlikely(!CMM_ACCESS_ONCE(__chan->session->active))) \
- return; \
- if (caa_unlikely(!CMM_ACCESS_ONCE(__chan->enabled))) \
- return; \
- if (caa_unlikely(!CMM_ACCESS_ONCE(__event->enabled))) \
+ if (caa_unlikely(!lttng_ust_do_trace(__chan->session, __chan, \
+ __event))) \
return; \
if (caa_unlikely(!TP_RCU_LINK_TEST())) \
return; \
diff --git a/liblttng-ust/lttng-context-perf-counters.c b/liblttng-ust/lttng-context-perf-counters.c
index a15417cc..131aaa54 100644
--- a/liblttng-ust/lttng-context-perf-counters.c
+++ b/liblttng-ust/lttng-context-perf-counters.c
@@ -291,6 +291,7 @@ struct lttng_perf_counter_thread_field *
ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
if (ret)
abort();
+ lttng_ust_begin_notrace();
/* Check again with signals disabled */
cds_list_for_each_entry_rcu(thread_field, &perf_thread->rcu_field_list,
rcu_field_node) {
@@ -315,6 +316,7 @@ struct lttng_perf_counter_thread_field *
&perf_field->thread_field_list);
ust_unlock();
skip:
+ lttng_ust_end_notrace();
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
if (ret)
abort();
diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
index 255c4b95..d8e4fd79 100644
--- a/liblttng-ust/lttng-events.c
+++ b/liblttng-ust/lttng-events.c
@@ -1284,3 +1284,17 @@ void lttng_ust_context_set_session_provider(const char *name,
}
}
}
+
+int lttng_ust_do_trace(struct lttng_session *session,
+ struct lttng_channel *chan, struct lttng_event *event)
+{
+ if (caa_unlikely(!CMM_ACCESS_ONCE(session->active)))
+ return 0;
+ if (caa_unlikely(!CMM_ACCESS_ONCE(chan->enabled)))
+ return 0;
+ if (caa_unlikely(!CMM_ACCESS_ONCE(event->enabled)))
+ return 0;
+ if (caa_unlikely(URCU_TLS(lttng_ust_notrace_thread)) > 0)
+ return 0;
+ return 1;
+}
diff --git a/liblttng-ust/lttng-tracer-core.h b/liblttng-ust/lttng-tracer-core.h
index ba232f32..98d79be8 100644
--- a/liblttng-ust/lttng-tracer-core.h
+++ b/liblttng-ust/lttng-tracer-core.h
@@ -25,6 +25,7 @@
#include <stddef.h>
#include <urcu/arch.h>
#include <urcu/list.h>
+#include <urcu/tls-compat.h>
#include <lttng/ust-tracer.h>
#include <lttng/bug.h>
#include <lttng/ringbuffer-config.h>
@@ -37,6 +38,8 @@ struct lttng_ctx_field;
struct lttng_ust_lib_ring_buffer_ctx;
struct lttng_ctx_value;
+extern DECLARE_URCU_TLS(int, lttng_ust_notrace_thread);
+
int ust_lock(void) __attribute__ ((warn_unused_result));
void ust_lock_nocheck(void);
void ust_unlock(void);
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index d4add1c0..9520f246 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -92,6 +92,9 @@ static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
/* Allow nesting the ust_mutex within the same thread. */
static DEFINE_URCU_TLS(int, ust_mutex_nest);
+/* Do not trace events for the current thread. */
+DEFINE_URCU_TLS(int, lttng_ust_notrace_thread) __attribute__((visibility("hidden")));
+
/*
* ust_exit_mutex protects thread_active variable wrt thread exit. It
* cannot be done by ust_mutex because pthread_cancel(), which takes an
@@ -121,6 +124,19 @@ static int lttng_ust_comm_should_quit;
int lttng_ust_loaded __attribute__((weak));
/*
+ * Inhibit lttng-ust tracing for this thread.
+ */
+void lttng_ust_begin_notrace(void)
+{
+ URCU_TLS(lttng_ust_notrace_thread)++;
+}
+
+void lttng_ust_end_notrace(void)
+{
+ --URCU_TLS(lttng_ust_notrace_thread);
+}
+
+/*
* Return 0 on success, -1 if should quit.
* The lock is taken in both cases.
* Signal-safe.
@@ -392,6 +408,12 @@ void lttng_fixup_ust_mutex_nest_tls(void)
asm volatile ("" : : "m" (URCU_TLS(ust_mutex_nest)));
}
+static
+void lttng_fixup_lttng_ust_notrace_tls(void)
+{
+ asm volatile ("" : : "m" (URCU_TLS(lttng_ust_notrace_thread)));
+}
+
/*
* Fixup urcu bp TLS.
*/
@@ -410,6 +432,7 @@ void lttng_ust_fixup_tls(void)
lttng_fixup_nest_count_tls();
lttng_fixup_procname_tls();
lttng_fixup_ust_mutex_nest_tls();
+ lttng_fixup_lttng_ust_notrace_tls();
lttng_ust_fixup_fd_tracker_tls();
}
--
2.11.0
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