Re: [PATCH 3/4] locking/lockdep: Reduce space occupied by stack traces

From: Bart Van Assche
Date: Wed Jul 24 2019 - 11:47:05 EST


On 7/23/19 9:56 PM, Eric Biggers wrote:
Does this also fix any of the other bugs listed at
https://lore.kernel.org/lkml/20190710055838.GC2152@xxxxxxxxxxxxxxx/
?

BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!
BUG: MAX_LOCKDEP_CHAINS too low!
BUG: MAX_LOCK_DEPTH too low! (2)
BUG: MAX_LOCKDEP_ENTRIES too low!

Hi Eric,

I don't think so. This patch only affects the space occupied by stack traces and not the space occupied by any of the other lockdep data strutures. BTW, in that report I found the following:

Title: BUG: MAX_LOCKDEP_CHAINS too low!
Last occurred: 5 days ago
Reported: 284 days ago

Title: BUG: MAX_LOCK_DEPTH too low! (2)
Last occurred: 362 days ago
Reported: 392 days ago

Since these bugs were reported more than 150 days ago these bugs are older than my lockdep changes and hence not a regression due to my lockdep changes.

My patch series did not increase the number of "list_entries" tracked by lockdep so I don't think that the "BUG: MAX_LOCKDEP_ENTRIES too low" behavior can be triggered more easily due to my lockdep changes.

The "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!" complaint however may be related. I will check whether it is possible to reduce the space occupied by held lock chains again to what was needed before my patch series.

Bart.