diff --git a/en_US.ISO8859-1/books/faq/book.sgml b/en_US.ISO8859-1/books/faq/book.sgml index 3f11a0bd93..3bb16946e1 100644 --- a/en_US.ISO8859-1/books/faq/book.sgml +++ b/en_US.ISO8859-1/books/faq/book.sgml @@ -3938,48 +3938,9 @@ kern.timecounter.hardware: TSC -> i8254 - &a.rwatson; answered this question very succinctly on - the freebsd-current list in a thread entitled lock - order reversals - what do they mean? - -
- &a.rwatson; on freebsd-current, December 14, - 2003 - - These warnings are generated by Witness, a run-time lock - diagnostic system found in FreeBSD -CURRENT kernels (but - removed in releases). You can read more about Witness in the - &man.witness.4; man page, which talks about its capabilities. Among - other things, Witness performs run-time lock order verification - using a combination of hard coded lock orders, and run-time - detected lock orders, and generates console warnings when lock - orders are violated. The intent of this is to detect the - potential for deadlocks due to lock order violations; it is worth - observing that Witness is actually slightly conservative, and so - it is possible to get false positives. In the event that Witness - is accurately reporting a lock order problem, it is basically - saying "If you were unlucky, a deadlock would have happened - here". There are a couple of "well known" false positives, - which we need to do a better job of documenting to prevent - spurious reports. The non-well-known ones typically correspond - to bugs in newly added locking, as lock order reversals usually - get fixed pretty quickly because Witness is busy generating - warnings :-). -
- - - A so-called "false positive" is actually Witness tripping - over a much more serious bug. Such bugs are typically a page - fault or memory corruption experienced inside of the kernel, or - a name clash with mutexes. - - - See Bjoern - Zeeb's lock order reversal page for the status of - known lock order reversals. - + An answer for this question can be found in the FreeBSD + Glosssary, see LOR.