diff mbox series

[v1,09/14] futex: Add sys_futex_requeue()

Message ID 20230721105744.298661259@infradead.org (mailing list archive)
State New
Headers show
Series futex: More futex2 bits | expand

Commit Message

Peter Zijlstra July 21, 2023, 10:22 a.m. UTC 
Finish of the 'simple' futex2 syscall group by adding
sys_futex_requeue(). Unlike sys_futex_{wait,wake}() it's arguments are
too numerous to fit into a regular syscall. As such, use struct
futex_waitv to pass the 'source' and 'destination' futexes to the
syscall.

This syscall implements what was previously known as FUTEX_CMP_REQUEUE
and uses {val, uaddr, flags} for source and {uaddr, flags} for
destination.

This design explicitly allows requeueing between different types of
futex by having a different flags word per uaddr.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/alpha/kernel/syscalls/syscall.tbl      |    1 
 arch/arm/tools/syscall.tbl                  |    1 
 arch/arm64/include/asm/unistd32.h           |    2 +
 arch/ia64/kernel/syscalls/syscall.tbl       |    1 
 arch/m68k/kernel/syscalls/syscall.tbl       |    1 
 arch/microblaze/kernel/syscalls/syscall.tbl |    1 
 arch/mips/kernel/syscalls/syscall_n32.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_n64.tbl   |    1 
 arch/mips/kernel/syscalls/syscall_o32.tbl   |    1 
 arch/parisc/kernel/syscalls/syscall.tbl     |    1 
 arch/powerpc/kernel/syscalls/syscall.tbl    |    1 
 arch/s390/kernel/syscalls/syscall.tbl       |    1 
 arch/sh/kernel/syscalls/syscall.tbl         |    1 
 arch/sparc/kernel/syscalls/syscall.tbl      |    1 
 arch/x86/entry/syscalls/syscall_32.tbl      |    1 
 arch/x86/entry/syscalls/syscall_64.tbl      |    1 
 arch/xtensa/kernel/syscalls/syscall.tbl     |    1 
 include/linux/syscalls.h                    |    3 ++
 include/uapi/asm-generic/unistd.h           |    4 ++
 kernel/futex/syscalls.c                     |   38 ++++++++++++++++++++++++++++
 kernel/sys_ni.c                             |    1 
 21 files changed, 63 insertions(+), 1 deletion(-)

Comments

Geert Uytterhoeven July 25, 2023, 7:23 a.m. UTC | #1 
On Fri, Jul 21, 2023 at 1:11 PM Peter Zijlstra <peterz@infradead.org> wrote:
> Finish of the 'simple' futex2 syscall group by adding
> sys_futex_requeue(). Unlike sys_futex_{wait,wake}() it's arguments are
> too numerous to fit into a regular syscall. As such, use struct
> futex_waitv to pass the 'source' and 'destination' futexes to the
> syscall.
>
> This syscall implements what was previously known as FUTEX_CMP_REQUEUE
> and uses {val, uaddr, flags} for source and {uaddr, flags} for
> destination.
>
> This design explicitly allows requeueing between different types of
> futex by having a different flags word per uaddr.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

>  arch/m68k/kernel/syscalls/syscall.tbl       |    1

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert
Thomas Gleixner July 31, 2023, 5:19 p.m. UTC | #2 
On Fri, Jul 21 2023 at 12:22, Peter Zijlstra wrote:
> +/*
> + * sys_futex_requeue - Requeue a waiter from one futex to another
> + * @waiters:	array describing the source and destination futex
> + * @flags:	unused
> + * @nr_wake:	number of futexes to wake
> + * @nr_requeue:	number of futexes to requeue
> + *
> + * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the
> + * futex2 family of calls.
> + */
> +
> +SYSCALL_DEFINE4(futex_requeue,
> +		struct futex_waitv __user *, waiters,
> +		unsigned int, flags,
> +		int, nr_wake,
> +		int, nr_requeue)
> +{
> +	struct futex_vector futexes[2];
> +	u32 cmpval;

So this is explictely u32. I'm completely confused vs. the 64 bit futex
size variant enablement earlier in the series by now.
Peter Zijlstra July 31, 2023, 5:38 p.m. UTC | #3 
On Mon, Jul 31, 2023 at 07:19:17PM +0200, Thomas Gleixner wrote:
> On Fri, Jul 21 2023 at 12:22, Peter Zijlstra wrote:
> > +/*
> > + * sys_futex_requeue - Requeue a waiter from one futex to another
> > + * @waiters:	array describing the source and destination futex
> > + * @flags:	unused
> > + * @nr_wake:	number of futexes to wake
> > + * @nr_requeue:	number of futexes to requeue
> > + *
> > + * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the
> > + * futex2 family of calls.
> > + */
> > +
> > +SYSCALL_DEFINE4(futex_requeue,
> > +		struct futex_waitv __user *, waiters,
> > +		unsigned int, flags,
> > +		int, nr_wake,
> > +		int, nr_requeue)
> > +{
> > +	struct futex_vector futexes[2];
> > +	u32 cmpval;
> 
> So this is explictely u32. I'm completely confused vs. the 64 bit futex
> size variant enablement earlier in the series by now.

As per the previous email; these patches only enable the syscall part of
64bit futexes, they do not convert the core, and per futex_flags_valid()
(patches 4 and 13), explicitly disallow having FUTEX2_64 set.


-       /* Only 32bit futexes are implemented -- for now */
-       if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
+       /* 64bit futexes aren't implemented -- yet */
+       if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
		return false;
diff mbox series

Patch

--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -493,3 +493,4 @@ 
 561	common	cachestat			sys_cachestat
 562	common	futex_wake			sys_futex_wake
 563	common	futex_wait			sys_futex_wait
+564	common	futex_requeue			sys_futex_requeue
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -467,3 +467,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -913,6 +913,8 @@  __SYSCALL(__NR_cachestat, sys_cachestat)
 __SYSCALL(__NR_futex_wake, sys_futex_wake)
 #define __NR_futex_wait 453
 __SYSCALL(__NR_futex_wait, sys_futex_wait)
+#define __NR_futex_requeue 454
+__SYSCALL(__NR_futex_requeue, sys_futex_requeue)
 
 /*
  * Please add new compat syscalls above this comment and update
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -374,3 +374,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -453,3 +453,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -459,3 +459,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -392,3 +392,4 @@ 
 451	n32	cachestat			sys_cachestat
 452	n32	futex_wake			sys_futex_wake
 453	n32	futex_wait			sys_futex_wait
+454	n32	futex_requeue			sys_futex_requeue
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -368,3 +368,4 @@ 
 451	n64	cachestat			sys_cachestat
 452	n64	futex_wake			sys_futex_wake
 453	n64	futex_wait			sys_futex_wait
+454	n64	futex_requeue			sys_futex_requeue
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -441,3 +441,4 @@ 
 451	o32	cachestat			sys_cachestat
 452	o32	futex_wake			sys_futex_wake
 453	o32	futex_wait			sys_futex_wait
+454	o32	futex_requeue			sys_futex_requeue
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -452,3 +452,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -540,3 +540,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -456,3 +456,4 @@ 
 451  common	cachestat		sys_cachestat			sys_cachestat
 452  common	futex_wake		sys_futex_wake			sys_futex_wake
 453  common	futex_wait		sys_futex_wait			sys_futex_wait
+454  common	futex_requeue		sys_futex_requeue			sys_futex_requeue
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -456,3 +456,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -499,3 +499,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -458,3 +458,4 @@ 
 451	i386	cachestat		sys_cachestat
 452	i386	futex_wake		sys_futex_wake
 453	i386	futex_wait		sys_futex_wait
+454	i386	futex_requeue		sys_futex_requeue
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -375,6 +375,7 @@ 
 451	common	cachestat		sys_cachestat
 452	common	futex_wake		sys_futex_wake
 453	common	futex_wait		sys_futex_wait
+454	common	futex_requeue		sys_futex_requeue
 
 #
 # Due to a historical design error, certain syscalls are numbered differently
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -424,3 +424,4 @@ 
 451	common	cachestat			sys_cachestat
 452	common	futex_wake			sys_futex_wake
 453	common	futex_wait			sys_futex_wait
+454	common	futex_requeue			sys_futex_requeue
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -570,6 +570,9 @@  asmlinkage long sys_futex_wait(void __us
 			       unsigned int flags, struct __kernel_timespec __user *timespec,
 			       clockid_t clockid);
 
+asmlinkage long sys_futex_requeue(struct futex_waitv __user *waiters,
+				  unsigned int flags, int nr_wake, int nr_requeue);
+
 asmlinkage long sys_nanosleep(struct __kernel_timespec __user *rqtp,
 			      struct __kernel_timespec __user *rmtp);
 asmlinkage long sys_nanosleep_time32(struct old_timespec32 __user *rqtp,
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -822,9 +822,11 @@  __SYSCALL(__NR_cachestat, sys_cachestat)
 __SYSCALL(__NR_futex_wake, sys_futex_wake)
 #define __NR_futex_wait 453
 __SYSCALL(__NR_futex_wait, sys_futex_wait)
+#define __NR_futex_requeue 454
+__SYSCALL(__NR_futex_requeue, sys_futex_requeue)
 
 #undef __NR_syscalls
-#define __NR_syscalls 454
+#define __NR_syscalls 455
 
 /*
  * 32 bit systems traditionally used different
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -396,6 +396,44 @@  SYSCALL_DEFINE6(futex_wait,
 	return ret;
 }
 
+/*
+ * sys_futex_requeue - Requeue a waiter from one futex to another
+ * @waiters:	array describing the source and destination futex
+ * @flags:	unused
+ * @nr_wake:	number of futexes to wake
+ * @nr_requeue:	number of futexes to requeue
+ *
+ * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the
+ * futex2 family of calls.
+ */
+
+SYSCALL_DEFINE4(futex_requeue,
+		struct futex_waitv __user *, waiters,
+		unsigned int, flags,
+		int, nr_wake,
+		int, nr_requeue)
+{
+	struct futex_vector futexes[2];
+	u32 cmpval;
+	int ret;
+
+	if (flags)
+		return -EINVAL;
+
+	if (!waiters)
+		return -EINVAL;
+
+	ret = futex_parse_waitv(futexes, waiters, 2);
+	if (ret)
+		return ret;
+
+	cmpval = futexes[0].w.val;
+
+	return futex_requeue(u64_to_user_ptr(futexes[0].w.uaddr), futexes[0].w.flags,
+			     u64_to_user_ptr(futexes[1].w.uaddr), futexes[1].w.flags,
+			     nr_wake, nr_requeue, &cmpval, 0);
+}
+
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE2(set_robust_list,
 		struct compat_robust_list_head __user *, head,
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -89,6 +89,7 @@  COND_SYSCALL_COMPAT(get_robust_list);
 COND_SYSCALL(futex_waitv);
 COND_SYSCALL(futex_wake);
 COND_SYSCALL(futex_wait);
+COND_SYSCALL(futex_requeue);
 COND_SYSCALL(kexec_load);
 COND_SYSCALL_COMPAT(kexec_load);
 COND_SYSCALL(init_module);