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author | Davidlohr Bueso <dave@stgolabs.net> | 2015-04-16 12:49:12 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-17 09:04:11 -0400 |
commit | 11163348a23cdbcdca5fb42485418e75f8566a5c (patch) | |
tree | 591adeddbcc89b51e047223b60b45500764fcc89 /kernel | |
parent | 15beb694c66146e1133b9ff81d54e3ef3daa1d7c (diff) | |
download | linux-stable-11163348a23cdbcdca5fb42485418e75f8566a5c.tar.gz linux-stable-11163348a23cdbcdca5fb42485418e75f8566a5c.tar.bz2 linux-stable-11163348a23cdbcdca5fb42485418e75f8566a5c.zip |
oprofile: reduce mmap_sem hold for mm->exe_file
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: Davidlohr Bueso <dbueso@suse.de>
Cc: Robert Richter <rric@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/fork.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 0d23e76a0c61..03c1eaaa6ef5 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -752,6 +752,7 @@ struct file *get_mm_exe_file(struct mm_struct *mm) rcu_read_unlock(); return exe_file; } +EXPORT_SYMBOL(get_mm_exe_file); /** * get_task_mm - acquire a reference to the task's mm |