lkml.org 
[lkml]   [2023]   [Aug]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
SubjectRe: [PATCH v2 05/14] futex: Add sys_futex_wake()
From
Hi Peter,

Em 07/08/2023 09:18, Peter Zijlstra escreveu:
> To complement sys_futex_waitv() add sys_futex_wake(). This syscall
> implements what was previously known as FUTEX_WAKE_BITSET except it
> uses 'unsigned long' for the bitmask and takes FUTEX2 flags.
>
> The 'unsigned long' allows FUTEX2_SIZE_U64 on 64bit platforms.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---

[...]

> +/*
> + * sys_futex_wake - Wake a number of futexes
> + * @uaddr: Address of the futex(es) to wake
> + * @mask: bitmask
> + * @nr: Number of the futexes to wake
> + * @flags: FUTEX2 flags
> + *
> + * Identical to the traditional FUTEX_WAKE_BITSET op, except it is part of the
> + * futex2 family of calls.
> + */
> +
> +SYSCALL_DEFINE4(futex_wake,
> + void __user *, uaddr,
> + unsigned long, mask,
> + int, nr,
> + unsigned int, flags)
> +{

Do you think we could have a

if (!nr)
return 0;

here? Otherwise, calling futex_wake(&f, 0, flags) will wake 1 futex (if
available), which is a strange undocumented behavior in my opinion.

> + if (flags & ~FUTEX2_VALID_MASK)
> + return -EINVAL;
> +
> + flags = futex2_to_flags(flags);
> + if (!futex_flags_valid(flags))
> + return -EINVAL;
> +
> + if (!futex_validate_input(flags, mask))
> + return -EINVAL;
> +
> + return futex_wake(uaddr, flags, nr, mask);
> +}
> +
> #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
> @@ -87,6 +87,7 @@ COND_SYSCALL_COMPAT(set_robust_list);
> COND_SYSCALL(get_robust_list);
> COND_SYSCALL_COMPAT(get_robust_list);
> COND_SYSCALL(futex_waitv);
> +COND_SYSCALL(futex_wake);
> COND_SYSCALL(kexec_load);
> COND_SYSCALL_COMPAT(kexec_load);
> COND_SYSCALL(init_module);
>
>

\
 
 \ /
  Last update: 2023-08-10 00:27    [W:0.107 / U:0.616 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site