Hi Roman,
Can you try the attached patch?
--HPS
Index: sys/kern/subr_epoch.c
===================================================================
--- sys/kern/subr_epoch.c (revision 336962)
+++ sys/kern/subr_epoch.c (working copy)
@@ -232,33 +232,14 @@
struct epoch_thread *tdwait;
struct turnstile *ts;
struct lock_object *lock;
- int spincount, gen;
int locksheld __unused;
record = __containerof(cr, struct epoch_record, er_record);
td = curthread;
locksheld = td->td_locks;
- spincount = 0;
counter_u64_add(block_count, 1);
if (record->er_cpuid != curcpu) {
/*
- * If the head of the list is running, we can wait for it
- * to remove itself from the list and thus save us the
- * overhead of a migration
- */
- if ((tdwait = TAILQ_FIRST(&record->er_tdlist)) != NULL &&
- TD_IS_RUNNING(tdwait->et_td)) {
- gen = record->er_gen;
- thread_unlock(td);
- do {
- cpu_spinwait();
- } while (tdwait == TAILQ_FIRST(&record->er_tdlist) &&
- gen == record->er_gen && TD_IS_RUNNING(tdwait->et_td) &&
- spincount++ < MAX_ADAPTIVE_SPIN);
- thread_lock(td);
- return;
- }
- /*
* Being on the same CPU as that of the record on which
* we need to wait allows us access to the thread
* list associated with that CPU. We can then examine the
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