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lockdep: add comments to mark_lock_irq()

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re-add some of the comments that got lost in the refactoring.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-01-27 14:53:50 +01:00 committed by Ingo Molnar
parent cf2ad4d13c
commit 38aa271438
1 changed files with 30 additions and 7 deletions
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33
kernel/lockdep.c
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@ -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) &&
/*
* 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;