| Message ID | 20171129154145.26755-3-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Nov 29, 2017 at 04:41:45PM +0100, Daniel Vetter wrote: > cross-release ftl > > From Chris: > > "Fwiw, this isn't cross-release but us reloading the module many times, > creating a whole host of new lockclasses. Even more fun is when the > module gets a slightly different address and the new lock address hashes > into an old lock... Yeah, this is a known issue, just reboot. > "I did think about a module-hook to revoke the stale lockclasses, but > that still leaves all the hashed chains. Its an absolute royal pain to remove all the resources consumed by a module, and if you manage you then have to deal with fragmented storage -- that is, we need to go keep track of which entries are used. Its a giant heap of complexity that's just not worth it. Given all that, I don't see why we should up this. Just don't reload modules (or better, don't use modules at all).
On Thu, Nov 30, 2017 at 08:47:18AM +0100, Peter Zijlstra wrote: > On Wed, Nov 29, 2017 at 04:41:45PM +0100, Daniel Vetter wrote: > > cross-release ftl > > > > From Chris: > > > > "Fwiw, this isn't cross-release but us reloading the module many times, > > creating a whole host of new lockclasses. Even more fun is when the > > module gets a slightly different address and the new lock address hashes > > into an old lock... > > Yeah, this is a known issue, just reboot. > > > "I did think about a module-hook to revoke the stale lockclasses, but > > that still leaves all the hashed chains. > > Its an absolute royal pain to remove all the resources consumed by a > module, and if you manage you then have to deal with fragmented storage > -- that is, we need to go keep track of which entries are used. > > Its a giant heap of complexity that's just not worth it. > > > Given all that, I don't see why we should up this. Just don't reload > modules (or better, don't use modules at all). We use excessive amounts of module reloading to validate the failure paths of driver load. Rebooting takes too much time. I guess we could look into just rebinding the driver without reloading, that should take the pain off lockdep. Meanwhile we can carry this locally. I just included this to check whether you have any plans, thanks for clarifying that this is not worth it from a core perspective to get fixed. The real issue we have in CI is the one the first patch papers over. -Daniel
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h index d459d624ba2a..41630a5385c6 100644 --- a/kernel/locking/lockdep_internals.h +++ b/kernel/locking/lockdep_internals.h @@ -69,7 +69,7 @@ enum { #else #define MAX_LOCKDEP_ENTRIES 32768UL -#define MAX_LOCKDEP_CHAINS_BITS 16 +#define MAX_LOCKDEP_CHAINS_BITS 17 /* * Stack-trace: tightly packed array of stack backtrace
cross-release ftl From Chris: "Fwiw, this isn't cross-release but us reloading the module many times, creating a whole host of new lockclasses. Even more fun is when the module gets a slightly different address and the new lock address hashes into an old lock... "I did think about a module-hook to revoke the stale lockclasses, but that still leaves all the hashed chains. "This particular nuisance was temporarily pushed back by teaching igt not to reload i915.ko on a whim." Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Marta Lofstedt <marta.lofstedt@intel.com> References: https://bugs.freedesktop.org/show_bug.cgi?id=103707 Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> --- kernel/locking/lockdep_internals.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)