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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@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20230921105248.511860556@noisy.programming.kicks-ass.net
This commit is contained in:
peterz@infradead.org 2023-09-21 12:45:15 +02:00 committed by Peter Zijlstra
parent 27b88f3519
commit 0f4b5f9722
22 changed files with 64 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/alpha/kernel/syscalls/syscall.tbl
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@ -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

1
arch/arm/tools/syscall.tbl
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@ -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

2
arch/arm64/include/asm/unistd.h
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@ -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

2
arch/arm64/include/asm/unistd32.h
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@ -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

1
arch/ia64/kernel/syscalls/syscall.tbl
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@ -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

1
arch/m68k/kernel/syscalls/syscall.tbl
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@ -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

1
arch/microblaze/kernel/syscalls/syscall.tbl
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@ -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

1
arch/mips/kernel/syscalls/syscall_n32.tbl
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@ -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

1
arch/mips/kernel/syscalls/syscall_n64.tbl
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@ -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

1
arch/mips/kernel/syscalls/syscall_o32.tbl
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@ -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

1
arch/parisc/kernel/syscalls/syscall.tbl
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@ -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

1
arch/powerpc/kernel/syscalls/syscall.tbl
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@ -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

1
arch/s390/kernel/syscalls/syscall.tbl
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@ -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

1
arch/sh/kernel/syscalls/syscall.tbl
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@ -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

1
arch/sparc/kernel/syscalls/syscall.tbl
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@ -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

1
arch/x86/entry/syscalls/syscall_32.tbl
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@ -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

1
arch/x86/entry/syscalls/syscall_64.tbl
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@ -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

1
arch/xtensa/kernel/syscalls/syscall.tbl
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@ -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

3
include/linux/syscalls.h
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@ -556,6 +556,9 @@ asmlinkage long sys_futex_wait(void __user *uaddr, unsigned long val, unsigned l
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,

4
include/uapi/asm-generic/unistd.h
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@ -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

38
kernel/futex/syscalls.c
View File

@ -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,

1
kernel/sys_ni.c
View File

@ -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);