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Merge branch 'sched-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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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 commit is contained in:
Linus Torvalds 2013-07-02 16:19:24 -07:00
commit e13053f506
11 changed files with 39 additions and 38 deletions
Download patch file Download diff file Expand all files Collapse all files

10
include/asm-generic/uaccess.h
View file

@ -163,7 +163,7 @@ static inline __must_check long __copy_to_user(void __user *to,
#define put_user(x, ptr) \
({ \
might_sleep(); \
might_fault(); \
access_ok(VERIFY_WRITE, ptr, sizeof(*ptr)) ? \
__put_user(x, ptr) : \
-EFAULT; \
@ -225,7 +225,7 @@ extern int __put_user_bad(void) __attribute__((noreturn));
#define get_user(x, ptr) \
({ \
might_sleep(); \
might_fault(); \
access_ok(VERIFY_READ, ptr, sizeof(*ptr)) ? \
__get_user(x, ptr) : \
-EFAULT; \
@ -255,7 +255,7 @@ extern int __get_user_bad(void) __attribute__((noreturn));
static inline long copy_from_user(void *to,
const void __user * from, unsigned long n)
{
might_sleep();
might_fault();
if (access_ok(VERIFY_READ, from, n))
return __copy_from_user(to, from, n);
else
@ -265,7 +265,7 @@ static inline long copy_from_user(void *to,
static inline long copy_to_user(void __user *to,
const void *from, unsigned long n)
{
might_sleep();
might_fault();
if (access_ok(VERIFY_WRITE, to, n))
return __copy_to_user(to, from, n);
else
@ -336,7 +336,7 @@ __clear_user(void __user *to, unsigned long n)
static inline __must_check unsigned long
clear_user(void __user *to, unsigned long n)
{
might_sleep();
might_fault();
if (!access_ok(VERIFY_WRITE, to, n))
return n;