Pull voluntary preemption fixes from Ingo Molnar:
"This tree contains a speedup which is achieved through better
might_sleep()/might_fault() preemption point annotations for uaccess
functions, by Michael S Tsirkin:
1. The only reason uaccess routines might sleep is if they fault.
Make this explicit for all architectures.
2. A voluntary preemption point in uaccess functions means compiler
can't inline them efficiently, this breaks assumptions that they
are very fast and small that e.g. net code seems to make. Remove
this preemption point so behaviour matches with what callers
assume.
3. Accesses (e.g through socket ops) to kernel memory with KERNEL_DS
like net/sunrpc does will never sleep. Remove an unconditinal
might_sleep() in the might_fault() inline in kernel.h (used when
PROVE_LOCKING is not set).
4. Accesses with pagefault_disable() return EFAULT but won't cause
caller to sleep. Check for that and thus avoid might_sleep() when
PROVE_LOCKING is set.
These changes offer a nice speedup for CONFIG_PREEMPT_VOLUNTARY=y
kernels, here's a network bandwidth measurement between a virtual
machine and the host:
before:
incoming: 7122.77 Mb/s
outgoing: 8480.37 Mb/s
after:
incoming: 8619.24 Mb/s [ +21.0% ]
outgoing: 9455.42 Mb/s [ +11.5% ]
I kept these changes in a separate tree, separate from scheduler
changes, because it's a mixed MM and scheduler topic"
* 'sched-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
mm, sched: Allow uaccess in atomic with pagefault_disable()
mm, sched: Drop voluntary schedule from might_fault()
x86: uaccess s/might_sleep/might_fault/
tile: uaccess s/might_sleep/might_fault/
powerpc: uaccess s/might_sleep/might_fault/
mn10300: uaccess s/might_sleep/might_fault/
microblaze: uaccess s/might_sleep/might_fault/
m32r: uaccess s/might_sleep/might_fault/
frv: uaccess s/might_sleep/might_fault/
arm64: uaccess s/might_sleep/might_fault/
asm-generic: uaccess s/might_sleep/might_fault/
This fixes the following compile error:
CC block/scsi_ioctl.o
block/scsi_ioctl.c: In function 'sg_scsi_ioctl':
block/scsi_ioctl.c:449: error: invalid initializer
Signed-off-by: David Howells <dhowells@redhat.com>
The only reason uaccess routines might sleep
is if they fault. Make this explicit.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1369577426-26721-6-git-send-email-mst@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
MN10300's asm/uaccess.h needs to #include linux/kernel.h to get might_sleep()
otherwise it fails to build on MN10300 allyesconfig. This fails in a few
places with messages like the following:
In file included from security/keys/trusted.c:14:
include/linux/uaccess.h: In function '__copy_from_user_nocache':
include/linux/uaccess.h:52: error: implicit declaration of function 'might_sleep'
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using __get_user_check(x, ptr++, size) leads to double increment of pointer.
This macro uses the macro get_user directly, which itself is used in this way
(get_user(x, ptr++)) in some functions of the kernel. The patch fixes the
error.
Reported-by: Tkhai Kirill <tkhai@yandex.ru>
Signed-off-by: David Howells <dhowells@redhat.com>
Save the current exception frame pointer in the thread_info struct rather than
in a global variable as the latter makes SMP tricky, especially when preemption
is also enabled.
This also replaces __frame with current_frame() and rearranges header file
inclusions to make it all compile.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Implement the Panasonic MN10300 AM34 CPU subarch and implement SMP support for
MN10300. Also implement support for the MN2WS0060 processor and the ASB2364
evaluation board which are AM34 based.
Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
gcc 4.2.1 for MN10300 is more agressive than the older gcc in
reordering/moving other insns between an insn that sets flags and an insn
that uses those flags. This leads to trouble with asm statements which
are missing an explicit "cc" clobber. This patch adds the explicit "cc"
clobber to asm statements which do indeed clobber the condition flags.
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix some build failures when using gcc-4.x for MN10300.
Firstly, __get_user() fails to build because the pointer points to a const and
__gu_val ends up being read-only:
In file included from include/linux/mempolicy.h:62,
from init/main.c:50:
include/linux/pagemap.h: In function 'fault_in_pages_readable':
include/linux/pagemap.h:394: error: read-only variable '__gu_val' used as 'asm' output
include/linux/pagemap.h:394: error: read-only variable '__gu_val' used as 'asm' output
include/linux/pagemap.h:394: error: read-only variable '__gu_val' used as 'asm' output
include/linux/pagemap.h:400: error: read-only variable '__gu_val' used as 'asm' output
include/linux/pagemap.h:400: error: read-only variable '__gu_val' used as 'asm' output
include/linux/pagemap.h:400: error: read-only variable '__gu_val' used as 'asm' output
make[1]: *** [init/main.o] Error 1
Secondly, gcc-4 doesn't allow casts of lvalues:
UPD include/linux/compile.h
arch/mn10300/kernel/rtc.c: In function 'calibrate_clock':
arch/mn10300/kernel/rtc.c:170: error: lvalue required as left operand of assignment
arch/mn10300/kernel/rtc.c:172: error: lvalue required as left operand of assignment
make[1]: *** [arch/mn10300/kernel/rtc.o] Error 1
These are seen with gcc 4.2.1.
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linus Torvalds