From 38aa2714382d886f77f2565277fce293122808b0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 27 Jan 2009 14:53:50 +0100 Subject: lockdep: add comments to mark_lock_irq() re-add some of the comments that got lost in the refactoring. Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- kernel/lockdep.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/kernel/lockdep.c b/kernel/lockdep.c index f40d916c191c..02e6e066d563 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -2054,6 +2054,9 @@ static int exclusive_bit(int new_bit) int state = new_bit & ~3; int dir = new_bit & 2; + /* + * keep state, bit flip the direction and strip read. + */ return state | (dir ^ 2); } @@ -2070,22 +2073,42 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this, int new_bit) int read = new_bit & 1; int dir = new_bit & 2; + /* + * mark USED_IN has to look forwards -- to ensure no dependency + * has ENABLED state, which would allow recursion deadlocks. + * + * mark ENABLED has to look backwards -- to ensure no dependee + * has USED_IN state, which, again, would allow recursion deadlocks. + */ check_usage_f usage = dir ? check_usage_backwards : check_usage_forwards; + /* + * Validate that this particular lock does not have conflicting + * usage states. + */ if (!valid_state(curr, this, new_bit, excl_bit)) return 0; - if (!read && !valid_state(curr, this, new_bit, excl_bit + 1)) - return 0; - - if ((!read || (!dir || STRICT_READ_CHECKS)) && + /* + * Validate that the lock dependencies don't have conflicting usage + * states. + */ + if ((!read || !dir || STRICT_READ_CHECKS) && !usage(curr, this, excl_bit, name)) return 0; - if ((!read && STRICT_READ_CHECKS) && - !usage(curr, this, excl_bit + 1, rname)) - return 0; + /* + * Check for read in write conflicts + */ + if (!read) { + if (!valid_state(curr, this, new_bit, excl_bit + 1)) + return 0; + + if (STRICT_READ_CHECKS && + !usage(curr, this, excl_bit + 1, rname)) + return 0; + } if (state_verbose(new_bit, hlock_class(this))) return 2; -- cgit v1.2.3