Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
futex: FLAGS_STRICT
The current semantics for futex_wake() are a bit loose, specifically
asking for 0 futexes to be woken actually gets you 1.
Adding a !nr check to sys_futex_wake() makes that it would return 0
for unaligned futex words, because that check comes in the shared
futex_wake() function. Adding the !nr check there, would affect the
legacy sys_futex() semantics.
Hence frob a flag :-(
Suggested-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230921105248.048643656@noisy.programming.kicks-ass.net
+15
-11
+11
-10
kernel/futex/futex.h
+11
-10
kernel/futex/futex.h
···
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* Futex flags used to encode options to functions and preserve them across
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* restarts.
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*/
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-
#define FLAGS_SIZE_8 0x00
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-
#define FLAGS_SIZE_16 0x01
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-
#define FLAGS_SIZE_32 0x02
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-
#define FLAGS_SIZE_64 0x03
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+
#define FLAGS_SIZE_8 0x0000
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+
#define FLAGS_SIZE_16 0x0001
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+
#define FLAGS_SIZE_32 0x0002
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+
#define FLAGS_SIZE_64 0x0003
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-
#define FLAGS_SIZE_MASK 0x03
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+
#define FLAGS_SIZE_MASK 0x0003
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#ifdef CONFIG_MMU
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-
# define FLAGS_SHARED 0x10
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+
# define FLAGS_SHARED 0x0010
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#else
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/*
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* NOMMU does not have per process address space. Let the compiler optimize
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* code away.
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*/
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-
# define FLAGS_SHARED 0x00
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+
# define FLAGS_SHARED 0x0000
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#endif
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-
#define FLAGS_CLOCKRT 0x20
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-
#define FLAGS_HAS_TIMEOUT 0x40
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-
#define FLAGS_NUMA 0x80
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+
#define FLAGS_CLOCKRT 0x0020
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+
#define FLAGS_HAS_TIMEOUT 0x0040
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+
#define FLAGS_NUMA 0x0080
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+
#define FLAGS_STRICT 0x0100
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/* FUTEX_ to FLAGS_ */
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static inline unsigned int futex_to_flags(unsigned int op)
+1
-1
kernel/futex/syscalls.c
+1
-1
kernel/futex/syscalls.c