• Johannes Weiner's avatar
    arch: mm: remove obsolete init OOM protection · 94bce453
    Johannes Weiner authored
    The memcg code can trap tasks in the context of the failing allocation
    until an OOM situation is resolved.  They can hold all kinds of locks
    (fs, mm) at this point, which makes it prone to deadlocking.
    
    This series converts memcg OOM handling into a two step process that is
    started in the charge context, but any waiting is done after the fault
    stack is fully unwound.
    
    Patches 1-4 prepare architecture handlers to support the new memcg
    requirements, but in doing so they also remove old cruft and unify
    out-of-memory behavior across architectures.
    
    Patch 5 disables the memcg OOM handling for syscalls, readahead, kernel
    faults, because they can gracefully unwind the stack with -ENOMEM.  OOM
    handling is restricted to user triggered faults that have no other
    option.
    
    Patch 6 reworks memcg's hierarchical OOM locking to make it a little
    more obvious wth is going on in there: reduce locked regions, rename
    locking functions, reorder and document.
    
    Patch 7 implements the two-part OOM handling such that tasks are never
    trapped with the full charge stack in an OOM situation.
    
    This patch:
    
    Back before smart OOM killing, when faulting tasks were killed directly on
    allocation failures, the arch-specific fault handlers needed special
    protection for the init process.
    
    Now that all fault handlers call into the generic OOM killer (see commit
    609838cf: "mm: invoke oom-killer from remaining unconverted page
    fault handlers"), which already provides init protection, the
    arch-specific leftovers can be removed.
    Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
    Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: azurIt <azurit@pobox.sk>
    Acked-by: Vineet Gupta <vgupta@synopsys.com>	[arch/arc bits]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    94bce453
fault.c 25.6 KB