• Huang Ying's avatar
    lib, Make gen_pool memory allocator lockless · 7f184275
    Huang Ying authored
    This version of the gen_pool memory allocator supports lockless
    operation.
    
    This makes it safe to use in NMI handlers and other special
    unblockable contexts that could otherwise deadlock on locks.  This is
    implemented by using atomic operations and retries on any conflicts.
    The disadvantage is that there may be livelocks in extreme cases.  For
    better scalability, one gen_pool allocator can be used for each CPU.
    
    The lockless operation only works if there is enough memory available.
    If new memory is added to the pool a lock has to be still taken.  So
    any user relying on locklessness has to ensure that sufficient memory
    is preallocated.
    
    The basic atomic operation of this allocator is cmpxchg on long.  On
    architectures that don't have NMI-safe cmpxchg implementation, the
    allocator can NOT be used in NMI handler.  So code uses the allocator
    in NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
    Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
    Reviewed-by: default avatarAndi Kleen <ak@linux.intel.com>
    Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLen Brown <len.brown@intel.com>
    7f184275
genalloc.h 3.15 KB