From: "Ondřej Surý via lttng-dev" <lttng-dev@lists.lttng.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: lttng-dev@lists.lttng.org, paulmck <paulmck@kernel.org>
Subject: Re: [lttng-dev] [PATCH 7/7] Experiment: Add explicit memory barrier in free_completion()
Date: Tue, 21 Mar 2023 11:21:10 +0100 [thread overview]
Message-ID: <A012AAA8-7E40-40A3-A272-1703EFA26314@sury.org> (raw)
In-Reply-To: <e7384cff-06a6-6e1e-9abc-ce7932760964@efficios.com>
> On 20. 3. 2023, at 19:37, Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>
> On 2023-03-17 17:37, Ondřej Surý via lttng-dev wrote:
>> FIXME: This is experiment that adds explicit memory barrier in the
>> free_completion in the workqueue.c, so ThreadSanitizer knows it's ok to
>> free the resources.
>> Signed-off-by: Ondřej Surý <ondrej@sury.org>
>> ---
>> src/workqueue.c | 1 +
>> 1 file changed, 1 insertion(+)
>> diff --git a/src/workqueue.c b/src/workqueue.c
>> index 1039d72..f21907f 100644
>> --- a/src/workqueue.c
>> +++ b/src/workqueue.c
>> @@ -377,6 +377,7 @@ void free_completion(struct urcu_ref *ref)
>> struct urcu_workqueue_completion *completion;
>> completion = caa_container_of(ref, struct urcu_workqueue_completion, ref);
>> + assert(!urcu_ref_get_unless_zero(&completion->ref));
>
> Perhaps what we really want here is an ANNOTATE_UNPUBLISH_MEMORY_RANGE() of some sort ?
I guess?
My experience with TSAN tells me, that you need some kind of memory barrier when using acquire-release
semantics and you do:
if (__atomic_sub_fetch(obj->ref, __ATOMIC_RELEASE) == 0) {
/* __ATOMIC_ACQUIRE needed here */
free(obj);
}
we end up using following code in BIND 9:
if (__atomic_sub_fetch(obj->ref, __ATOMIC_ACQ_REL) == 0) {
free(obj);
}
So, I am guessing after the change of uatomic_sub_return() to __ATOMIC_ACQ_REL,
this patch should no longer be needed.
Ondrej
--
Ondřej Surý (He/Him)
ondrej@sury.org
_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
next prev parent reply other threads:[~2023-03-21 10:21 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-17 21:37 [lttng-dev] [PATCH 0/7] Replace the custom code with gcc/clang __atomic builtins Ondřej Surý via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 1/7] Require __atomic builtins to build Ondřej Surý via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 2/7] Use gcc __atomic builtis for <urcu/uatomic.h> implementation Ondřej Surý via lttng-dev
2023-03-20 18:03 ` Mathieu Desnoyers via lttng-dev
2023-03-20 18:13 ` Mathieu Desnoyers via lttng-dev
2023-03-20 18:28 ` Ondřej Surý via lttng-dev
2023-03-20 18:38 ` Mathieu Desnoyers via lttng-dev
2023-03-20 18:41 ` Mathieu Desnoyers via lttng-dev
2023-03-20 19:38 ` Duncan Sands via lttng-dev
2023-03-21 20:26 ` Mathieu Desnoyers via lttng-dev
2023-03-22 8:24 ` Duncan Sands via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 3/7] Use __atomic_thread_fence() for cmm_barrier() Ondřej Surý via lttng-dev
2023-03-20 18:06 ` Mathieu Desnoyers via lttng-dev
2023-03-20 18:14 ` Mathieu Desnoyers via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 4/7] Replace the internal pointer manipulation with __atomic builtins Ondřej Surý via lttng-dev
2023-03-20 18:25 ` Mathieu Desnoyers via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 5/7] Use __atomic builtins to implement CMM_{LOAD, STORE}_SHARED Ondřej Surý via lttng-dev
2023-03-20 18:28 ` Mathieu Desnoyers via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 6/7] Fix: uatomic_or() need retyping to uintptr_t in rculfhash.c Ondřej Surý via lttng-dev
2023-03-20 18:31 ` Mathieu Desnoyers via lttng-dev
2023-03-21 10:15 ` Ondřej Surý via lttng-dev
2023-03-21 14:44 ` Mathieu Desnoyers via lttng-dev
2023-03-21 14:45 ` Mathieu Desnoyers via lttng-dev
2023-03-17 21:37 ` [lttng-dev] [PATCH 7/7] Experiment: Add explicit memory barrier in free_completion() Ondřej Surý via lttng-dev
2023-03-20 18:37 ` Mathieu Desnoyers via lttng-dev
2023-03-21 10:21 ` Ondřej Surý via lttng-dev [this message]
2023-03-21 14:46 ` Mathieu Desnoyers via lttng-dev
2023-03-21 14:48 ` Ondřej Surý via lttng-dev
2023-03-21 14:49 ` Mathieu Desnoyers via lttng-dev
2023-03-21 14:59 ` [lttng-dev] TSAN and the tests Ondřej Surý via lttng-dev
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=A012AAA8-7E40-40A3-A272-1703EFA26314@sury.org \
--to=lttng-dev@lists.lttng.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=ondrej@sury.org \
--cc=paulmck@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).