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>,
"André Almeida" <andrealmeid@collabora.com>
Subject: [PATCH v4 15/15] kernel: Enable waitpid() for futex2
Date: Thu, 3 Jun 2021 16:59:24 -0300 [thread overview]
Message-ID: <20210603195924.361327-16-andrealmeid@collabora.com> (raw)
In-Reply-To: <20210603195924.361327-1-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 c108df6b3b82..94e0356ceeaa 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1324,6 +1324,8 @@ 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 long 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 dc06afd725cb..344430d882b1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1322,6 +1322,8 @@ 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 5fd0b3d73b53..bf2de369b78a 100644
--- a/kernel/futex2.c
+++ b/kernel/futex2.c
@@ -978,18 +978,8 @@ static inline bool futex_match(struct futex_key key1, struct futex_key key2)
key1.offset == key2.offset);
}
-/**
- * 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 long nr_wake,
+ unsigned int flags)
{
bool shared = (flags & FUTEX_SHARED_FLAG) ? true : false;
unsigned int size = flags & FUTEX_SIZE_MASK;
@@ -1023,6 +1013,22 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake,
return ret;
}
+/**
+ * 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);
+}
+
static void futex_double_unlock(struct futex_bucket *b1, struct futex_bucket *b2)
{
spin_unlock(&b1->lock);
--
2.31.1
next prev parent reply other threads:[~2021-06-03 20:01 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-03 19:59 [PATCH v4 00/15] Add futex2 syscalls André Almeida
2021-06-03 19:59 ` [PATCH v4 01/15] futex2: Implement wait and wake functions André Almeida
2021-06-03 19:59 ` [PATCH v4 02/15] futex2: Add support for shared futexes André Almeida
2021-06-03 19:59 ` [PATCH v4 03/15] futex2: Implement vectorized wait André Almeida
2021-06-03 19:59 ` [PATCH v4 04/15] futex2: Implement requeue operation André Almeida
2021-06-03 19:59 ` [PATCH v4 05/15] futex2: Implement support for different futex sizes André Almeida
2021-06-04 0:23 ` kernel test robot
2021-06-06 19:12 ` Davidlohr Bueso
2021-06-06 23:01 ` Andrey Semashev
2021-06-03 19:59 ` [PATCH v4 06/15] futex2: Add compatibility entry point for x86_x32 ABI André Almeida
2021-06-03 19:59 ` [PATCH v4 07/15] docs: locking: futex2: Add documentation André Almeida
2021-06-06 19:23 ` Davidlohr Bueso
2021-06-03 19:59 ` [PATCH v4 08/15] selftests: futex2: Add wake/wait test André Almeida
2021-06-03 19:59 ` [PATCH v4 09/15] selftests: futex2: Add timeout test André Almeida
2021-06-03 19:59 ` [PATCH v4 10/15] selftests: futex2: Add wouldblock test André Almeida
2021-06-03 19:59 ` [PATCH v4 11/15] selftests: futex2: Add waitv test André Almeida
2021-06-03 19:59 ` [PATCH v4 12/15] selftests: futex2: Add requeue test André Almeida
2021-06-03 19:59 ` [PATCH v4 13/15] selftests: futex2: Add futex sizes test André Almeida
2021-06-03 19:59 ` [PATCH v4 14/15] perf bench: Add futex2 benchmark tests André Almeida
2021-06-03 19:59 ` André Almeida [this message]
2021-06-04 4:51 ` [PATCH v4 00/15] Add futex2 syscalls Zebediah Figura
2021-06-04 17:04 ` André Almeida
2021-06-04 11:36 ` Nicholas Piggin
2021-06-04 20:01 ` André Almeida
2021-06-05 1:09 ` Nicholas Piggin
2021-06-05 8:56 ` Andrey Semashev
2021-06-06 11:57 ` Nicholas Piggin
2021-06-06 13:15 ` Andrey Semashev
2021-06-08 1:25 ` Nicholas Piggin
2021-06-08 11:03 ` Andrey Semashev
2021-06-08 11:13 ` Greg KH
2021-06-08 11:44 ` Peter Zijlstra
2021-06-08 14:31 ` Davidlohr Bueso
2021-06-08 12:06 ` Andrey Semashev
2021-06-08 12:33 ` Greg KH
2021-06-08 12:35 ` Greg KH
2021-06-08 13:18 ` Andrey Semashev
2021-06-08 13:27 ` Greg KH
2021-06-08 13:41 ` Andrey Semashev
2021-06-08 17:06 ` Zebediah Figura
2021-06-08 14:14 ` André Almeida
2021-06-07 15:40 ` André Almeida
2021-06-08 1:31 ` Nicholas Piggin
2021-06-08 2:33 ` Davidlohr Bueso
2021-06-08 4:45 ` Nicholas Piggin
2021-06-08 12:26 ` Sebastian Andrzej Siewior
2021-06-08 14:23 ` Peter Zijlstra
2021-06-08 14:57 ` Sebastian Andrzej Siewior
2021-06-08 15:04 ` André Almeida
2021-06-08 18:08 ` Adhemerval Zanella
2021-06-08 18:19 ` Florian Weimer
2021-06-08 18:22 ` Adhemerval Zanella
2021-06-09 16:26 ` David Laight
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