• D
    oprofile: reduce mmap_sem hold for mm->exe_file · 11163348
    Davidlohr Bueso 提交于
    sync_buffer() needs the mmap_sem for two distinct operations, both only
    occurring upon user context switch handling:
    
     1) Dealing with the exe_file.
    
     2) Adding the dcookie data as we need to lookup the vma that
       backs it. This is done via add_sample() and add_data().
    
    This patch isolates 1), for it will no longer need the mmap_sem for
    serialization.  However, for now, make of the more standard
    get_mm_exe_file(), requiring only holding the mmap_sem to read the value,
    and relying on reference counting to make sure that the exe file won't
    dissappear underneath us while doing the get dcookie.
    
    As a consequence, for 2) we move the mmap_sem locking into where we really
    need it, in lookup_dcookie().  The benefits are twofold: reduce mmap_sem
    hold times, and cleaner code.
    
    [akpm@linux-foundation.org: export get_mm_exe_file for arch/x86/oprofile/oprofile.ko]
    Signed-off-by: NDavidlohr Bueso <dbueso@suse.de>
    Cc: Robert Richter <rric@kernel.org>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    11163348
fork.c 49.5 KB