[PATCH v3 10/15] futex: Add sys_futex_requeue()

From: peterz
Date: Thu Sep 21 2023 - 15:31:03 EST

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In reply to: Thomas Gleixner: "Re: [PATCH v3 06/15] futex: FLAGS_STRICT"
Next in thread: tip-bot2 for peterz@xxxxxxxxxxxxx: "[tip: locking/core] futex: Add sys_futex_requeue()"
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Finish off the 'simple' futex2 syscall group by adding
sys_futex_requeue(). Unlike sys_futex_{wait,wake}() its 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@xxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
arch/alpha/kernel/syscalls/syscall.tbl | 1
arch/arm/tools/syscall.tbl | 1
arch/arm64/include/asm/unistd.h | 2 -
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
22 files changed, 64 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/alpha/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/alpha/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/alpha/kernel/syscalls/syscall.tbl
@@ -494,3 +494,4 @@
562 common fchmodat2 sys_fchmodat2
563 common futex_wake sys_futex_wake
564 common futex_wait sys_futex_wait
+565 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/arm/tools/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/arm/tools/syscall.tbl
+++ linux-2.6/arch/arm/tools/syscall.tbl
@@ -468,3 +468,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/arm64/include/asm/unistd.h
===================================================================
--- linux-2.6.orig/arch/arm64/include/asm/unistd.h
+++ linux-2.6/arch/arm64/include/asm/unistd.h
@@ -39,7 +39,7 @@
#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)

-#define __NR_compat_syscalls 456
+#define __NR_compat_syscalls 457
#endif

#define __ARCH_WANT_SYS_CLONE
Index: linux-2.6/arch/arm64/include/asm/unistd32.h
===================================================================
--- linux-2.6.orig/arch/arm64/include/asm/unistd32.h
+++ linux-2.6/arch/arm64/include/asm/unistd32.h
@@ -915,6 +915,8 @@ __SYSCALL(__NR_fchmodat2, sys_fchmodat2)
__SYSCALL(__NR_futex_wake, sys_futex_wake)
#define __NR_futex_wait 455
__SYSCALL(__NR_futex_wait, sys_futex_wait)
+#define __NR_futex_requeue 456
+__SYSCALL(__NR_futex_requeue, sys_futex_requeue)

/*
* Please add new compat syscalls above this comment and update
Index: linux-2.6/arch/ia64/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/ia64/kernel/syscalls/syscall.tbl
@@ -375,3 +375,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/m68k/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/m68k/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/m68k/kernel/syscalls/syscall.tbl
@@ -454,3 +454,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/microblaze/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/microblaze/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -460,3 +460,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/mips/kernel/syscalls/syscall_n32.tbl
===================================================================
--- linux-2.6.orig/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ linux-2.6/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -393,3 +393,4 @@
452 n32 fchmodat2 sys_fchmodat2
454 n32 futex_wake sys_futex_wake
455 n32 futex_wait sys_futex_wait
+456 n32 futex_requeue sys_futex_requeue
Index: linux-2.6/arch/mips/kernel/syscalls/syscall_n64.tbl
===================================================================
--- linux-2.6.orig/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ linux-2.6/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -369,3 +369,4 @@
452 n64 fchmodat2 sys_fchmodat2
454 n64 futex_wake sys_futex_wake
455 n64 futex_wait sys_futex_wait
+456 n64 futex_requeue sys_futex_requeue
Index: linux-2.6/arch/mips/kernel/syscalls/syscall_o32.tbl
===================================================================
--- linux-2.6.orig/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ linux-2.6/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -442,3 +442,4 @@
452 o32 fchmodat2 sys_fchmodat2
454 o32 futex_wake sys_futex_wake
455 o32 futex_wait sys_futex_wait
+456 o32 futex_requeue sys_futex_requeue
Index: linux-2.6/arch/parisc/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/parisc/kernel/syscalls/syscall.tbl
@@ -453,3 +453,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/powerpc/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -541,3 +541,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/s390/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/s390/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/s390/kernel/syscalls/syscall.tbl
@@ -457,3 +457,4 @@
452 common fchmodat2 sys_fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue sys_futex_requeue
Index: linux-2.6/arch/sh/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/sh/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/sh/kernel/syscalls/syscall.tbl
@@ -457,3 +457,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/sparc/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/sparc/kernel/syscalls/syscall.tbl
@@ -500,3 +500,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/arch/x86/entry/syscalls/syscall_32.tbl
===================================================================
--- linux-2.6.orig/arch/x86/entry/syscalls/syscall_32.tbl
+++ linux-2.6/arch/x86/entry/syscalls/syscall_32.tbl
@@ -459,3 +459,4 @@
452 i386 fchmodat2 sys_fchmodat2
454 i386 futex_wake sys_futex_wake
455 i386 futex_wait sys_futex_wait
+456 i386 futex_requeue sys_futex_requeue
Index: linux-2.6/arch/x86/entry/syscalls/syscall_64.tbl
===================================================================
--- linux-2.6.orig/arch/x86/entry/syscalls/syscall_64.tbl
+++ linux-2.6/arch/x86/entry/syscalls/syscall_64.tbl
@@ -377,6 +377,7 @@
453 64 map_shadow_stack sys_map_shadow_stack
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue

#
# Due to a historical design error, certain syscalls are numbered differently
Index: linux-2.6/arch/xtensa/kernel/syscalls/syscall.tbl
===================================================================
--- linux-2.6.orig/arch/xtensa/kernel/syscalls/syscall.tbl
+++ linux-2.6/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -425,3 +425,4 @@
452 common fchmodat2 sys_fchmodat2
454 common futex_wake sys_futex_wake
455 common futex_wait sys_futex_wait
+456 common futex_requeue sys_futex_requeue
Index: linux-2.6/include/linux/syscalls.h
===================================================================
--- linux-2.6.orig/include/linux/syscalls.h
+++ linux-2.6/include/linux/syscalls.h
@@ -556,6 +556,9 @@ 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,
Index: linux-2.6/include/uapi/asm-generic/unistd.h
===================================================================
--- linux-2.6.orig/include/uapi/asm-generic/unistd.h
+++ linux-2.6/include/uapi/asm-generic/unistd.h
@@ -826,9 +826,11 @@ __SYSCALL(__NR_fchmodat2, sys_fchmodat2)
__SYSCALL(__NR_futex_wake, sys_futex_wake)
#define __NR_futex_wait 455
__SYSCALL(__NR_futex_wait, sys_futex_wait)
+#define __NR_futex_requeue 456
+__SYSCALL(__NR_futex_requeue, sys_futex_requeue)

#undef __NR_syscalls
-#define __NR_syscalls 456
+#define __NR_syscalls 457

/*
* 32 bit systems traditionally used different
Index: linux-2.6/kernel/futex/syscalls.c
===================================================================
--- linux-2.6.orig/kernel/futex/syscalls.c
+++ linux-2.6/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,
Index: linux-2.6/kernel/sys_ni.c
===================================================================
--- linux-2.6.orig/kernel/sys_ni.c
+++ linux-2.6/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);

Next message: Huangzheng Lai: "[PATCH V2 6/7] i2c: sprd: Increase the waiting time for I2C transmission to avoid system crash issues"
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In reply to: Thomas Gleixner: "Re: [PATCH v3 06/15] futex: FLAGS_STRICT"
Next in thread: tip-bot2 for peterz@xxxxxxxxxxxxx: "[tip: locking/core] futex: Add sys_futex_requeue()"
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