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authorByungchul Park <byungchul.park@lge.com>2017-08-14 16:00:51 +0900
committerIngo Molnar <mingo@kernel.org>2017-08-14 12:52:17 +0200
commita10b5c564741cd3b6708f085a1fa892b63c2063d (patch)
tree40d6e4d2ee27832eefd092b5a538ec035a12df80 /kernel/locking/lockdep.c
parentccde85ba00cccd28436e19c5bf503165c55a04f3 (diff)
locking/lockdep: Add a comment about crossrelease_hist_end() in lockdep_sys_exit()
In lockdep_sys_exit(), crossrelease_hist_end() is called unconditionally even when getting here without having started e.g. just after forking. But it's no problem since it would roll back to an invalid entry anyway. Add a comment to explain this. Signed-off-by: Byungchul Park <byungchul.park@lge.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akpm@linux-foundation.org Cc: boqun.feng@gmail.com Cc: kernel-team@lge.com Cc: kirill@shutemov.name Cc: linux-mm@kvack.org Cc: npiggin@gmail.com Cc: walken@google.com Cc: willy@infradead.org Link: http://lkml.kernel.org/r/1502694052-16085-2-git-send-email-byungchul.park@lge.com [ Improved the description and the comments. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking/lockdep.c')
-rw-r--r--kernel/locking/lockdep.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1114dc42c27f..257931e2fbbe 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4623,6 +4623,10 @@ asmlinkage __visible void lockdep_sys_exit(void)
/*
* The lock history for each syscall should be independent. So wipe the
* slate clean on return to userspace.
+ *
+ * crossrelease_hist_end() works well here even when getting here
+ * without starting (i.e. just after forking), because it rolls back
+ * the index to point to the last entry, which is already invalid.
*/
crossrelease_hist_end(XHLOCK_PROC);
crossrelease_hist_start(XHLOCK_PROC);