releases/3.10.61/arch-mm-remove-obsolete-init-oom-protection.patch

   1 From 94bce453c78996cc4373d5da6cfabe07fcc6d9f9 Mon Sep 17 00:00:00 2001
   2 From: Johannes Weiner <hannes@cmpxchg.org>
   3 Date: Thu, 12 Sep 2013 15:13:36 -0700
   4 Subject: arch: mm: remove obsolete init OOM protection
   5
   6 From: Johannes Weiner <hannes@cmpxchg.org>
   7
   8 commit 94bce453c78996cc4373d5da6cfabe07fcc6d9f9 upstream.
   9
  10 The memcg code can trap tasks in the context of the failing allocation
  11 until an OOM situation is resolved.  They can hold all kinds of locks
  12 (fs, mm) at this point, which makes it prone to deadlocking.
  13
  14 This series converts memcg OOM handling into a two step process that is
  15 started in the charge context, but any waiting is done after the fault
  16 stack is fully unwound.
  17
  18 Patches 1-4 prepare architecture handlers to support the new memcg
  19 requirements, but in doing so they also remove old cruft and unify
  20 out-of-memory behavior across architectures.
  21
  22 Patch 5 disables the memcg OOM handling for syscalls, readahead, kernel
  23 faults, because they can gracefully unwind the stack with -ENOMEM.  OOM
  24 handling is restricted to user triggered faults that have no other
  25 option.
  26
  27 Patch 6 reworks memcg's hierarchical OOM locking to make it a little
  28 more obvious wth is going on in there: reduce locked regions, rename
  29 locking functions, reorder and document.
  30
  31 Patch 7 implements the two-part OOM handling such that tasks are never
  32 trapped with the full charge stack in an OOM situation.
  33
  34 This patch:
  35
  36 Back before smart OOM killing, when faulting tasks were killed directly on
  37 allocation failures, the arch-specific fault handlers needed special
  38 protection for the init process.
  39
  40 Now that all fault handlers call into the generic OOM killer (see commit
  41 609838cfed97: "mm: invoke oom-killer from remaining unconverted page
  42 fault handlers"), which already provides init protection, the
  43 arch-specific leftovers can be removed.
  44
  45 Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
  46 Reviewed-by: Michal Hocko <mhocko@suse.cz>
  47 Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
  48 Cc: David Rientjes <rientjes@google.com>
  49 Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
  50 Cc: azurIt <azurit@pobox.sk>
  51 Acked-by: Vineet Gupta <vgupta@synopsys.com>    [arch/arc bits]
  52 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  53 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  54 Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
  55 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  56
  57 ---
  58  arch/arc/mm/fault.c   |    5 -----
  59  arch/score/mm/fault.c |    6 ------
  60  arch/tile/mm/fault.c  |    6 ------
  61  3 files changed, 17 deletions(-)
  62
  63 --- a/arch/arc/mm/fault.c
  64 +++ b/arch/arc/mm/fault.c
  65 @@ -120,7 +120,6 @@ good_area:
  66                         goto bad_area;
  67         }
  68
  69 -survive:
  70         /*
  71          * If for any reason at all we couldn't handle the fault,
  72          * make sure we exit gracefully rather than endlessly redo
  73 @@ -200,10 +199,6 @@ no_context:
  74         die("Oops", regs, address, cause_code);
  75
  76  out_of_memory:
  77 -       if (is_global_init(tsk)) {
  78 -               yield();
  79 -               goto survive;
  80 -       }
  81         up_read(&mm->mmap_sem);
  82
  83         if (user_mode(regs)) {
  84 --- a/arch/score/mm/fault.c
  85 +++ b/arch/score/mm/fault.c
  86 @@ -100,7 +100,6 @@ good_area:
  87                         goto bad_area;
  88         }
  89
  90 -survive:
  91         /*
  92         * If for any reason at all we couldn't handle the fault,
  93         * make sure we exit gracefully rather than endlessly redo
  94 @@ -167,11 +166,6 @@ no_context:
  95         */
  96  out_of_memory:
  97         up_read(&mm->mmap_sem);
  98 -       if (is_global_init(tsk)) {
  99 -               yield();
 100 -               down_read(&mm->mmap_sem);
 101 -               goto survive;
 102 -       }
 103         if (!user_mode(regs))
 104                 goto no_context;
 105         pagefault_out_of_memory();
 106 --- a/arch/tile/mm/fault.c
 107 +++ b/arch/tile/mm/fault.c
 108 @@ -430,7 +430,6 @@ good_area:
 109                         goto bad_area;
 110         }
 111
 112 - survive:
 113         /*
 114          * If for any reason at all we couldn't handle the fault,
 115          * make sure we exit gracefully rather than endlessly redo
 116 @@ -568,11 +567,6 @@ no_context:
 117   */
 118  out_of_memory:
 119         up_read(&mm->mmap_sem);
 120 -       if (is_global_init(tsk)) {
 121 -               yield();
 122 -               down_read(&mm->mmap_sem);
 123 -               goto survive;
 124 -       }
 125         if (is_kernel_mode)
 126                 goto no_context;
 127         pagefault_out_of_memory();