linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "André Almeida" <andrealmeid@collabora.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <dvhart@infradead.org>,
	linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: kernel@collabora.com, krisman@collabora.com,
	pgriffais@valvesoftware.com, z.figura12@gmail.com,
	joel@joelfernandes.org, malteskarupke@fastmail.fm,
	linux-api@vger.kernel.org, fweimer@redhat.com,
	libc-alpha@sourceware.org, linux-kselftest@vger.kernel.org,
	shuah@kernel.org, acme@kernel.org, corbet@lwn.net,
	"Peter Oskolkov" <posk@posk.io>,
	"Andrey Semashev" <andrey.semashev@gmail.com>,
	"Davidlohr Bueso" <dave@stgolabs.net>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Adhemerval Zanella" <adhemerval.zanella@linaro.org>,
	"André Almeida" <andrealmeid@collabora.com>
Subject: [PATCH v5 11/11] kernel: Enable waitpid() for futex2
Date: Thu,  8 Jul 2021 21:13:28 -0300	[thread overview]
Message-ID: <20210709001328.329716-12-andrealmeid@collabora.com> (raw)
In-Reply-To: <20210709001328.329716-1-andrealmeid@collabora.com>

To make pthreads works as expected if they are using futex2, wake
clear_child_tid with futex2 as well. This is make applications that uses
waitpid() (and clone(CLONE_CHILD_SETTID)) wake while waiting for the
child to terminate. Given that apps should not mix futex() and futex2(),
any correct app will trigger a harmless noop wakeup on the interface
that it isn't using.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
---

This commit is here for the intend to show what we need to do in order
to get a full NPTL working on top of futex2. It should be merged after
we talk to glibc folks on the details around the futex_wait() side. For
instance, we could use this as an opportunity to use private futexes or
8bit sized futexes, but both sides need to use the exactly same flags.
---
 include/linux/syscalls.h |  2 ++
 kernel/fork.c            |  2 ++
 kernel/futex2.c          | 30 ++++++++++++++++++------------
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index b9c2874410d0..85b5a501fb96 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1315,6 +1315,8 @@ int ksys_ipc(unsigned int call, int first, unsigned long second,
 	unsigned long third, void __user * ptr, long fifth);
 int compat_ksys_ipc(u32 call, int first, int second,
 	u32 third, u32 ptr, u32 fifth);
+long ksys_futex_wake(void __user *uaddr, unsigned int nr_wake,
+		     unsigned int flags);
 
 /*
  * The following kernel syscall equivalents are just wrappers to fs-internal
diff --git a/kernel/fork.c b/kernel/fork.c
index b4386ff6a641..f3f98e197fb6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1328,6 +1328,8 @@ static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 			put_user(0, tsk->clear_child_tid);
 			do_futex(tsk->clear_child_tid, FUTEX_WAKE,
 					1, NULL, NULL, 0, 0);
+			ksys_futex_wake(tsk->clear_child_tid, 1,
+					FUTEX_32 | FUTEX_SHARED_FLAG);
 		}
 		tsk->clear_child_tid = NULL;
 	}
diff --git a/kernel/futex2.c b/kernel/futex2.c
index 4f6d099badec..2ca2f40fcdd2 100644
--- a/kernel/futex2.c
+++ b/kernel/futex2.c
@@ -420,18 +420,8 @@ COMPAT_SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, compat_u64, val,
 }
 #endif
 
-/**
- * sys_futex_wake - Wake a number of futexes waiting on an address
- * @uaddr:   Address of futex to be woken up
- * @nr_wake: Number of futexes waiting in uaddr to be woken up
- * @flags:   Flags for size and shared
- *
- * Wake `nr_wake` threads waiting at uaddr.
- *
- * Returns the number of woken threads on success, error code otherwise.
- */
-SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake,
-		unsigned int, flags)
+long ksys_futex_wake(void __user *uaddr, unsigned int nr_wake,
+		     unsigned int flags)
 {
 	unsigned int size = flags & FUTEX_SIZE_MASK, futex_flags = 0;
 
@@ -447,6 +437,22 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake,
 	return futex_wake(uaddr, futex_flags, nr_wake, FUTEX_BITSET_MATCH_ANY);
 }
 
+/**
+ * sys_futex_wake - Wake a number of futexes waiting on an address
+ * @uaddr:   Address of futex to be woken up
+ * @nr_wake: Number of futexes waiting in uaddr to be woken up
+ * @flags:   Flags for size and shared
+ *
+ * Wake `nr_wake` threads waiting at uaddr.
+ *
+ * Returns the number of woken threads on success, error code otherwise.
+ */
+SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake,
+		unsigned int, flags)
+{
+	return ksys_futex_wake(uaddr, nr_wake, flags);
+}
+
 #ifdef CONFIG_COMPAT
 static int compat_futex_parse_requeue(struct compat_futex_requeue __user *rq,
 				      void __user **uaddr, unsigned int *flags)
-- 
2.32.0


      parent reply	other threads:[~2021-07-09  0:15 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09  0:13 [PATCH v5 00/11] Add futex2 syscalls André Almeida
2021-07-09  0:13 ` [PATCH v5 01/11] futex2: Implement wait and wake functions André Almeida
2021-07-09  0:13 ` [PATCH v5 02/11] futex2: Implement vectorized wait André Almeida
2021-07-14 21:19   ` Gabriel Krisman Bertazi
2021-08-17  8:50   ` Arnd Bergmann
2021-08-18 16:20     ` André Almeida
2021-07-09  0:13 ` [PATCH v5 03/11] futex2: Implement requeue operation André Almeida
2021-07-09  0:13 ` [PATCH v5 04/11] docs: locking: futex2: Add documentation André Almeida
2021-07-14 21:25   ` Gabriel Krisman Bertazi
2021-07-09  0:13 ` [PATCH v5 05/11] selftests: futex2: Add wake/wait test André Almeida
2021-07-09  0:13 ` [PATCH v5 06/11] selftests: futex2: Add timeout test André Almeida
2021-07-09  0:13 ` [PATCH v5 07/11] selftests: futex2: Add wouldblock test André Almeida
2021-07-09  0:13 ` [PATCH v5 08/11] selftests: futex2: Add waitv test André Almeida
2021-07-09  0:13 ` [PATCH v5 09/11] selftests: futex2: Add requeue test André Almeida
2021-07-09  0:13 ` [PATCH v5 10/11] perf bench: Add futex2 benchmark tests André Almeida
2021-07-09  0:13 ` André Almeida [this message]

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=20210709001328.329716-12-andrealmeid@collabora.com \
    --to=andrealmeid@collabora.com \
    --cc=acme@kernel.org \
    --cc=adhemerval.zanella@linaro.org \
    --cc=andrey.semashev@gmail.com \
    --cc=bigeasy@linutronix.de \
    --cc=corbet@lwn.net \
    --cc=dave@stgolabs.net \
    --cc=dvhart@infradead.org \
    --cc=fweimer@redhat.com \
    --cc=joel@joelfernandes.org \
    --cc=kernel@collabora.com \
    --cc=krisman@collabora.com \
    --cc=libc-alpha@sourceware.org \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=malteskarupke@fastmail.fm \
    --cc=mingo@redhat.com \
    --cc=npiggin@gmail.com \
    --cc=peterz@infradead.org \
    --cc=pgriffais@valvesoftware.com \
    --cc=posk@posk.io \
    --cc=rostedt@goodmis.org \
    --cc=shuah@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=z.figura12@gmail.com \
    --subject='Re: [PATCH v5 11/11] kernel: Enable waitpid() for futex2' \
    /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

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox