linux-toradex.git/arch/arc/include/asm/futex.h, branch v4.10

ARC: change some branchs to jumps to resolve linkage errors

2015-08-20T13:23:15+00:00

When kernel's binary becomes large enough (32M and more) errors
may occur during the final linkage stage. It happens because
the build system uses short relocations for ARC  by default.
This problem may be easily resolved by passing -mlong-calls
option to GCC to use long absolute jumps (j) instead of short
relative branchs (b).

But there are fragments of pure assembler code exist which use
branchs in inappropriate places and cause a linkage error because
of relocations overflow.

First of these fragments is .fixup insertion in futex.h and
unaligned.c. It inserts a code in the separate section (.fixup)
with branch instruction. It leads to the linkage error when
kernel becomes large.

Second of these fragments is calling scheduler's functions
(common kernel code) from entry.S of ARC's code. When kernel's
binary becomes large it may lead to the linkage error because
scheduler may occur far enough from ARC's code in the final
binary.

Signed-off-by: Yuriy Kolerov 
Signed-off-by: Vineet Gupta

ARC: ensure futex ops are atomic in !LLSC config

2015-08-20T12:46:01+00:00

W/o hardware assisted atomic r-m-w the best we can do is to disable
preemption.

Cc: David Hildenbrand 
Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: Michel Lespinasse 
Signed-off-by: Vineet Gupta

ARC: make futex_atomic_cmpxchg_inatomic() return bimodal

2015-08-20T12:46:00+00:00

Callers of cmpxchg_futex_value_locked() in futex code expect bimodal
return value:
  !0 (essentially -EFAULT as failure)
   0 (success)

Before this patch, the success return value was old value of futex,
which could very well be non zero, causing caller to possibly take the
failure path erroneously.

Fix that by returning 0 for success

(This fix was done back in 2011 for all upstream arches, which ARC
obviously missed)

Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: Michel Lespinasse 
Signed-off-by: Vineet Gupta

ARC: futex cosmetics

2015-08-20T12:46:00+00:00

Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: Michel Lespinasse 
Signed-off-by: Vineet Gupta

ARC: add barriers to futex code

2015-08-20T12:45:59+00:00

The atomic ops on futex need to provide the full barrier just like
regular atomics in kernel.

Also remove pagefault_enable/disable in futex_atomic_cmpxchg_inatomic()
as core code already does that

Cc: David Hildenbrand 
Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: Michel Lespinasse 
Signed-off-by: Vineet Gupta

ARC: Add llock/scond to futex backend

2015-07-09T12:06:33+00:00

Signed-off-by: Vineet Gupta

sched/preempt, futex: Update comments to clarify that preemption doesn't have to be disabled

2015-05-19T06:39:17+00:00

As arm64 and arc have no special implementations for !CONFIG_SMP, mutual
exclusion doesn't seem to rely on preemption.

Let's make it clear in the comments that preemption doesn't have to be
disabled when accessing user space in the futex code, so we can remove
preempt_disable() from pagefault_disable().

Reviewed-and-tested-by: Thomas Gleixner 
Signed-off-by: David Hildenbrand 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
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/1431359540-32227-13-git-send-email-dahi@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar

ARC: Futex support

2013-02-15T17:46:00+00:00

Signed-off-by: Vineet Gupta