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authorDavidlohr Bueso <dave@stgolabs.net>2015-04-16 12:49:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-17 09:04:11 -0400
commit11163348a23cdbcdca5fb42485418e75f8566a5c (patch)
tree591adeddbcc89b51e047223b60b45500764fcc89 /kernel/fork.c
parent15beb694c66146e1133b9ff81d54e3ef3daa1d7c (diff)
downloadlinux-sh-11163348a23cdbcdca5fb42485418e75f8566a5c.tar.gz
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/fork.c')
-rw-r--r--kernel/fork.c1
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