Commit-ID: a10b5c564741cd3b6708f085a1fa892b63c2063d Gitweb: http://git.kernel.org/tip/a10b5c564741cd3b6708f085a1fa892b63c2063d Author: Byungchul Park <byungchul.park@xxxxxxx> AuthorDate: Mon, 14 Aug 2017 16:00:51 +0900 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Mon, 14 Aug 2017 12:52:17 +0200 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@xxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: akpm@xxxxxxxxxxxxxxxxxxxx Cc: boqun.feng@xxxxxxxxx Cc: kernel-team@xxxxxxx Cc: kirill@xxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Cc: npiggin@xxxxxxxxx Cc: walken@xxxxxxxxxx Cc: willy@xxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1502694052-16085-2-git-send-email-byungchul.park@xxxxxxx [ Improved the description and the comments. ] Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/locking/lockdep.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 1114dc4..257931e 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); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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