From: tip-bot for David Hildenbrand <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, hpa@zytor.com, torvalds@linux-foundation.org,
tglx@linutronix.de, linux-kernel@vger.kernel.org,
dahi@linux.vnet.ibm.com, peterz@infradead.org
Subject: [tip:sched/core] sched/preempt, arm/futex: Disable preemption in UP futex_atomic_op_inuser() explicitly
Date: Tue, 19 May 2015 00:21:23 -0700 [thread overview]
Message-ID: <tip-388b0e0adbc98a1b12a077dc92851a3ce016db42@git.kernel.org> (raw)
In-Reply-To: <1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com>
Commit-ID: 388b0e0adbc98a1b12a077dc92851a3ce016db42
Gitweb: http://git.kernel.org/tip/388b0e0adbc98a1b12a077dc92851a3ce016db42
Author: David Hildenbrand <dahi@linux.vnet.ibm.com>
AuthorDate: Mon, 11 May 2015 17:52:16 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 May 2015 08:39:17 +0200
sched/preempt, arm/futex: Disable preemption in UP futex_atomic_op_inuser() explicitly
The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely
on disabled preemption to guarantee mutual exclusion.
>From commit e589ed23dd27 ("[ARM] 5218/1: arm: improved futex support"):
"For UP it's enough to disable preemption to ensure mutual exclusion..."
>From the code itself:
"!SMP, we can work around lack of atomic ops by disabling preemption"
Let's make this explicit, to prepare for pagefault_disable() not
touching preemption anymore.
Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: benh@kernel.crashing.org
Cc: bigeasy@linutronix.de
Cc: borntraeger@de.ibm.com
Cc: daniel.vetter@intel.com
Cc: heiko.carstens@de.ibm.com
Cc: herbert@gondor.apana.org.au
Cc: hocko@suse.cz
Cc: hughd@google.com
Cc: mst@redhat.com
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: schwidefsky@de.ibm.com
Cc: yang.shi@windriver.com
Link: http://lkml.kernel.org/r/1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/arm/include/asm/futex.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index 255bfd1..5eed828 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -127,7 +127,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
- pagefault_disable(); /* implies preempt_disable() */
+#ifndef CONFIG_SMP
+ preempt_disable();
+#endif
+ pagefault_disable();
switch (op) {
case FUTEX_OP_SET:
@@ -149,7 +152,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
ret = -ENOSYS;
}
- pagefault_enable(); /* subsumes preempt_enable() */
+ pagefault_enable();
+#ifndef CONFIG_SMP
+ preempt_enable();
+#endif
if (!ret) {
switch (cmp) {
next prev parent reply other threads:[~2015-05-19 7:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-11 15:52 [PATCH v1 00/15] decouple pagefault_disable() from preempt_disable() David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 01/15] uaccess: count pagefault_disable() levels in pagefault_disabled David Hildenbrand
2015-05-19 7:18 ` [tip:sched/core] sched/preempt, mm/fault: Count pagefault_disable () " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 02/15] mm, uaccess: trigger might_sleep() in might_fault() with disabled pagefaults David Hildenbrand
2015-05-19 7:18 ` [tip:sched/core] sched/preempt, mm/fault: Trigger " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 03/15] uaccess: clarify that uaccess may only sleep if pagefaults are enabled David Hildenbrand
2015-05-19 7:18 ` [tip:sched/core] mm/uaccess, mm/fault: Clarify " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 04/15] mm: explicitly disable/enable preemption in kmap_atomic_* David Hildenbrand
2015-05-19 7:19 ` [tip:sched/core] sched/preempt, mm/kmap: Explicitly disable/ enable " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 05/15] mips: kmap_coherent relies on disabled preemption David Hildenbrand
2015-05-19 7:19 ` [tip:sched/core] sched/preempt, mm/kmap, MIPS: Disable preemption in kmap_coherent() explicitly tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 06/15] mm: use pagefault_disable() to check for disabled pagefaults in the handler David Hildenbrand
2015-05-19 7:19 ` [tip:sched/core] mm/fault, arch: Use " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 07/15] drm/i915: use pagefault_disabled() to check for disabled pagefaults David Hildenbrand
2015-05-19 7:20 ` [tip:sched/core] mm/fault, drm/i915: Use " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 08/15] futex: UP futex_atomic_op_inuser() relies on disabled preemption David Hildenbrand
2015-05-19 7:20 ` [tip:sched/core] sched/preempt, futex: Disable preemption in UP futex_atomic_op_inuser() explicitly tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 09/15] futex: UP futex_atomic_cmpxchg_inatomic() relies on disabled preemption David Hildenbrand
2015-05-19 7:20 ` [tip:sched/core] sched/preempt, futex: Disable preemption in UP futex_atomic_cmpxchg_inatomic() explicitly tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 10/15] arm/futex: UP futex_atomic_cmpxchg_inatomic() relies on disabled preemption David Hildenbrand
2015-05-19 7:21 ` [tip:sched/core] sched/preempt, arm/futex: Disable preemption in UP futex_atomic_cmpxchg_inatomic() explicitly tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 11/15] arm/futex: UP futex_atomic_op_inuser() relies on disabled preemption David Hildenbrand
2015-05-12 19:00 ` Sebastian Andrzej Siewior
2015-05-13 7:38 ` David Hildenbrand
2015-05-13 8:19 ` Sebastian Andrzej Siewior
2015-05-13 8:55 ` David Hildenbrand
2015-05-19 7:21 ` tip-bot for David Hildenbrand [this message]
2015-05-11 15:52 ` [PATCH v1 12/15] futex: clarify that preemption doesn't have to be disabled David Hildenbrand
2015-05-19 7:21 ` [tip:sched/core] sched/preempt, futex: Update comments to " tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 13/15] powerpc: enable_kernel_altivec() requires disabled preemption David Hildenbrand
2015-05-19 7:22 ` [tip:sched/core] sched/preempt, powerpc: Disable preemption in enable_kernel_altivec() explicitly tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 14/15] mips: properly lock access to the fpu David Hildenbrand
2015-05-19 7:22 ` [tip:sched/core] sched/preempt, MIPS: Properly lock access to the FPU tip-bot for David Hildenbrand
2015-05-11 15:52 ` [PATCH v1 15/15] uaccess: decouple preemption from the pagefault logic David Hildenbrand
2015-05-19 7:22 ` [tip:sched/core] sched/preempt, mm/fault: Decouple preemption from the page fault logic tip-bot for David Hildenbrand
2015-05-15 14:23 ` [PATCH v1 00/15] decouple pagefault_disable() from preempt_disable() Thomas Gleixner
2015-05-18 12:46 ` David Hildenbrand
2015-05-18 13:04 ` Peter Zijlstra
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