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,
"André Almeida" <andrealmeid@collabora.com>
Subject: [RFC PATCH v2 13/13] kernel: Enable waitpid() for futex2
Date: Wed, 3 Mar 2021 21:42:19 -0300 [thread overview]
Message-ID: <20210304004219.134051-14-andrealmeid@collabora.com> (raw)
In-Reply-To: <20210304004219.134051-1-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 b0675f236066..b07b7d4334a6 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1316,6 +1316,8 @@ 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 d66cd1014211..e39846a73a43 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1308,6 +1308,8 @@ 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 92b560206666..dd6f54ae0220 100644
--- a/kernel/futex2.c
+++ b/kernel/futex2.c
@@ -924,18 +924,8 @@ 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;
@@ -972,6 +962,22 @@ 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);
--
2.30.1
next prev parent reply other threads:[~2021-03-04 1:09 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 0:42 [RFC PATCH v2 00/13] Add futex2 syscall André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 01/13] futex2: Implement wait and wake functions André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 02/13] futex2: Add support for shared futexes André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 03/13] futex2: Implement vectorized wait André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 04/13] futex2: Implement requeue operation André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 05/13] futex2: Add compatibility entry point for x86_x32 ABI André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 06/13] docs: locking: futex2: Add documentation André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 07/13] selftests: futex2: Add wake/wait test André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 08/13] selftests: futex2: Add timeout test André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 09/13] selftests: futex2: Add wouldblock test André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 10/13] selftests: futex2: Add waitv test André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 11/13] selftests: futex2: Add requeue test André Almeida
2021-03-04 0:42 ` [RFC PATCH v2 12/13] perf bench: Add futex2 benchmark tests André Almeida
2021-03-04 0:42 ` André Almeida [this message]
2021-03-04 5:44 ` [RFC PATCH v2 00/13] Add futex2 syscall Peter Oskolkov
2021-03-04 18:58 ` André Almeida
2021-03-05 20:03 ` Peter Oskolkov
2021-03-05 20:08 ` Peter Oskolkov
2021-03-04 15:01 ` Theodore Ts'o
2021-03-04 19:15 ` André Almeida
2021-03-07 11:34 ` Stefan Metzmacher
2021-03-07 11:56 ` Daurnimator
2021-03-08 11:52 ` Stefan Metzmacher
2021-03-08 11:11 ` David Laight
2021-03-08 11:55 ` Stefan Metzmacher
2021-03-08 16:18 ` Zebediah Figura
2021-03-08 17:33 ` David Laight
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