linux/arch/powerpc
Christoph Hellwig dacbe41f77 ptrace: move user_enable_single_step & co prototypes to linux/ptrace.h
While in theory user_enable_single_step/user_disable_single_step/
user_enable_blockstep could also be provided as an inline or macro there's
no good reason to do so, and having the prototype in one places keeps code
size and confusion down.

Roland said:

  The original thought there was that user_enable_single_step() et al
  might well be only an instruction or three on a sane machine (as if we
  have any of those!), and since there is only one call site inlining
  would be beneficial.  But I agree that there is no strong reason to care
  about inlining it.

  As to the arch changes, there is only one thought I'd add to the
  record.  It was always my thinking that for an arch where
  PTRACE_SINGLESTEP does text-modifying breakpoint insertion,
  user_enable_single_step() should not be provided.  That is,
  arch_has_single_step()=>true means that there is an arch facility with
  "pure" semantics that does not have any unexpected side effects.
  Inserting a breakpoint might do very unexpected strange things in
  multi-threaded situations.  Aside from that, it is a peculiar side
  effect that user_{enable,disable}_single_step() should cause COW
  de-sharing of text pages and so forth.  For PTRACE_SINGLESTEP, all these
  peculiarities are the status quo ante for that arch, so having
  arch_ptrace() itself do those is one thing.  But for building other
  things in the future, it is nicer to have a uniform "pure" semantics
  that arch-independent code can expect.

  OTOH, all such arch issues are really up to the arch maintainer.  As
  of today, there is nothing but ptrace using user_enable_single_step() et
  al so it's a distinction without a practical difference.  If/when there
  are other facilities that use user_enable_single_step() and might care,
  the affected arch's can revisit the question when someone cares about
  the quality of the arch support for said new facility.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-03-12 15:52:38 -08:00
..
boot Merge branch 'master' of /home/davem/src/GIT/linux-2.6/ 2010-02-28 19:23:06 -08:00
configs Merge branch 'master' of /home/davem/src/GIT/linux-2.6/ 2010-02-28 19:23:06 -08:00
include/asm ptrace: move user_enable_single_step & co prototypes to linux/ptrace.h 2010-03-12 15:52:38 -08:00
kernel Add generic sys_olduname() 2010-03-12 15:52:32 -08:00
kvm Merge branch 'kvm-updates/2.6.34' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2010-03-05 13:12:34 -08:00
lib powerpc: Fix lwsync feature fixup vs. modules on 64-bit 2010-02-26 18:29:17 +11:00
math-emu powerpc/math-emu: Fix efp dependence 2009-03-11 06:00:08 -05:00
mm nodemask.h: remove macro any_online_node 2010-03-06 11:26:31 -08:00
oprofile tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
platforms [WATCHDOG] watchdog_info constify 2010-03-07 10:30:57 +00:00
sysdev Merge commit 'origin/master' into next 2010-02-26 14:41:00 +11:00
xmon powerpc: Mark some variables in the page fault path __read_mostly 2010-02-03 17:39:48 +11:00
Kconfig Merge commit 'origin/master' into next 2010-02-26 14:41:00 +11:00
Kconfig.debug Merge branch 'next' of git://git.secretlab.ca/git/linux-2.6 2009-12-16 13:26:53 -08:00
Makefile powerpc: Check for unsupported relocs when using CONFIG_RELOCATABLE 2009-09-24 15:31:40 +10:00
relocs_check.pl powerpc: Check for unsupported relocs when using CONFIG_RELOCATABLE 2009-09-24 15:31:40 +10:00