Re: [PATCH v2 05/14] futex: Add sys_futex_wake()
From: André Almeida <andrealmeid@igalia.com>
Date: 2023-08-09 22:25:35
Also in:
linux-arch, linux-mm, lkml
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.
quoted hunk ↗ jump to hunk
+ 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);