From: peterz@infradead.org
To: tglx@linutronix.de, axboe@kernel.dk
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net,
andrealmeid@igalia.com, Andrew Morton <akpm@linux-foundation.org>,
urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com,
Arnd Bergmann <arnd@arndb.de>,
linux-api@vger.kernel.org, linux-mm@kvack.org,
linux-arch@vger.kernel.org, malteskarupke@web.de
Subject: [PATCH v3 06/15] futex: FLAGS_STRICT
Date: Thu, 21 Sep 2023 12:45:11 +0200 [thread overview]
Message-ID: <20230921105248.048643656@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20230921104505.717750284@noisy.programming.kicks-ass.net>
[-- Attachment #1: peterz-futex2-wake-0.patch --]
[-- Type: text/plain, Size: 2516 bytes --]
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>
---
Index: linux-2.6/kernel/futex/futex.h
===================================================================
--- linux-2.6.orig/kernel/futex/futex.h
+++ linux-2.6/kernel/futex/futex.h
@@ -17,25 +17,26 @@
* Futex flags used to encode options to functions and preserve them across
* restarts.
*/
-#define FLAGS_SIZE_8 0x00
-#define FLAGS_SIZE_16 0x01
-#define FLAGS_SIZE_32 0x02
-#define FLAGS_SIZE_64 0x03
+#define FLAGS_SIZE_8 0x0000
+#define FLAGS_SIZE_16 0x0001
+#define FLAGS_SIZE_32 0x0002
+#define FLAGS_SIZE_64 0x0003
-#define FLAGS_SIZE_MASK 0x03
+#define FLAGS_SIZE_MASK 0x0003
#ifdef CONFIG_MMU
-# define FLAGS_SHARED 0x10
+# define FLAGS_SHARED 0x0010
#else
/*
* NOMMU does not have per process address space. Let the compiler optimize
* code away.
*/
-# define FLAGS_SHARED 0x00
+# define FLAGS_SHARED 0x0000
#endif
-#define FLAGS_CLOCKRT 0x20
-#define FLAGS_HAS_TIMEOUT 0x40
-#define FLAGS_NUMA 0x80
+#define FLAGS_CLOCKRT 0x0020
+#define FLAGS_HAS_TIMEOUT 0x0040
+#define FLAGS_NUMA 0x0080
+#define FLAGS_STRICT 0x0100
/* FUTEX_ to FLAGS_ */
static inline unsigned int futex_to_flags(unsigned int op)
Index: linux-2.6/kernel/futex/syscalls.c
===================================================================
--- linux-2.6.orig/kernel/futex/syscalls.c
+++ linux-2.6/kernel/futex/syscalls.c
@@ -333,7 +333,7 @@ SYSCALL_DEFINE4(futex_wake,
if (!futex_validate_input(flags, mask))
return -EINVAL;
- return futex_wake(uaddr, flags, nr, mask);
+ return futex_wake(uaddr, FLAGS_STRICT | flags, nr, mask);
}
#ifdef CONFIG_COMPAT
Index: linux-2.6/kernel/futex/waitwake.c
===================================================================
--- linux-2.6.orig/kernel/futex/waitwake.c
+++ linux-2.6/kernel/futex/waitwake.c
@@ -155,6 +155,9 @@ int futex_wake(u32 __user *uaddr, unsign
if (unlikely(ret != 0))
return ret;
+ if ((flags & FLAGS_STRICT) && !nr_wake)
+ return 0;
+
hb = futex_hash(&key);
/* Make sure we really have tasks to wakeup */
next prev parent reply other threads:[~2023-09-21 11:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 10:45 [PATCH v3 00/15] futex: More futex2 bits peterz
2023-09-21 10:45 ` [PATCH v3 01/15] futex: Clarify FUTEX2 flags peterz
2023-09-21 10:45 ` [PATCH v3 02/15] futex: Extend the " peterz
2023-09-21 10:45 ` [PATCH v3 03/15] futex: Flag conversion peterz
2023-09-21 10:45 ` [PATCH v3 04/15] futex: Validate futex value against futex size peterz
2023-09-21 10:45 ` [PATCH v3 05/15] futex: Add sys_futex_wake() peterz
2023-09-21 10:45 ` peterz [this message]
2023-09-21 15:14 ` [PATCH v3 06/15] futex: FLAGS_STRICT Thomas Gleixner
2023-09-21 10:45 ` [PATCH v3 07/15] futex: Add sys_futex_wait() peterz
2023-09-21 10:45 ` [PATCH v3 08/15] futex: Propagate flags into get_futex_key() peterz
2023-09-21 10:45 ` [PATCH v3 09/15] futex: Add flags2 argument to futex_requeue() peterz
2023-09-21 10:45 ` [PATCH v3 10/15] futex: Add sys_futex_requeue() peterz
2023-09-22 9:35 ` Ingo Molnar
2023-09-22 11:03 ` Peter Zijlstra
2023-09-22 13:56 ` Jens Axboe
2023-09-21 10:45 ` [PATCH v3 11/15] mm: Add vmalloc_huge_node() peterz
2023-09-21 10:45 ` [PATCH v3 12/15] futex: Implement FUTEX2_NUMA peterz
2023-09-21 10:45 ` [PATCH v3 13/15] futex: Propagate flags into futex_get_value_locked() peterz
2023-09-21 10:45 ` [PATCH v3 14/15] futex: Enable FUTEX2_{8,16} peterz
2023-09-21 10:45 ` [PATCH v3 15/15] futex,selftests: Extend the futex selftests peterz
2023-09-21 11:41 ` Peter Zijlstra
2023-09-22 20:01 ` futex2 numa stuff Peter Zijlstra
2023-09-22 20:01 ` [PATCH 15/15] futex,selftests: Extend the futex selftests Peter Zijlstra
2023-09-22 20:01 ` [PATCH 16/15] futex,selftests: Extend the futex selftests for NUMA Peter Zijlstra
2023-09-22 20:01 ` [PATCH 17/15] [HACK] futex: Force futex hash collision Peter Zijlstra
2023-09-28 13:40 ` futex2 numa stuff Davidlohr Bueso
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230921105248.048643656@noisy.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=andrealmeid@igalia.com \
--cc=arnd@arndb.de \
--cc=axboe@kernel.dk \
--cc=dave@stgolabs.net \
--cc=dvhart@infradead.org \
--cc=hch@infradead.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lstoakes@gmail.com \
--cc=malteskarupke@web.de \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--cc=urezki@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox