From 1b253694f47c4874bc53483823ec570ea253b321 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Tue, 20 Oct 2015 20:29:21 +0000 Subject: [PATCH] Mark struct thread zone as type-stable. When establishing the locking state for several lock types (including blockable mutexes and sx) failed, locking primitives try to spin while the owner thread is running. The spinning loop performs the test for running condition by dereferencing the owner->td_state field of the owner thread. If the owner thread exited while spinner was put off the processor, it is harmless to access reused struct thread owner, since in some near future the current processor would notice the owner change and make appropriate progress. But it could be that the page which carried the freed struct thread was unmapped, then we fault (this cannot happen on amd64). For now, disallowing free of the struct thread seems to be good enough, and tests which create a lot of threads once, did not demonstrated regressions. Reviewed by: jhb, pho Reported and tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D3908 --- sys/kern/kern_thread.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c index 3c6232cc1e21..ac96ca504539 100644 --- a/sys/kern/kern_thread.c +++ b/sys/kern/kern_thread.c @@ -281,7 +281,7 @@ threadinit(void) thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), thread_ctor, thread_dtor, thread_init, thread_fini, - 16 - 1, 0); + 16 - 1, UMA_ZONE_NOFREE); tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); rw_init(&tidhash_lock, "tidhash"); }