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Convert epoch to read / write records per cpu
In discussing D17503 "Run epoch calls sooner and more reliably" with sbahra@ we came to the conclusion that epoch is currently misusing the ck_epoch API. It isn't safe to do a "write side" operation (ck_epoch_call or ck_epoch_poll) in the middle of a "read side" section. Since, by definition, it's possible to be preempted during the middle of an EPOCH_PREEMPT epoch the GC task might call ck_epoch_poll or another thread might call ck_epoch_call on the same section. The right solution is ultimately to change the way that ck_epoch works for this use case. However, as a stopgap for 12 we agreed to simply have separate records for each use case. Tested by: pho@ MFC after: 3 days
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parent
b4d66a1739
commit
10f42d244b
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=340097
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@ -150,7 +150,8 @@ epoch_ctor(epoch_t epoch)
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CPU_FOREACH(cpu) {
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er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
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bzero(er, sizeof(*er));
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ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL);
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ck_epoch_register(&epoch->e_epoch, &er->er_read_record, NULL);
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ck_epoch_register(&epoch->e_epoch, &er->er_write_record, NULL);
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TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist);
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er->er_cpuid = cpu;
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}
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@ -235,7 +236,7 @@ epoch_block_handler_preempt(struct ck_epoch *global __unused, ck_epoch_record_t
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int spincount, gen;
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int locksheld __unused;
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record = __containerof(cr, struct epoch_record, er_record);
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record = __containerof(cr, struct epoch_record, er_read_record);
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td = curthread;
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locksheld = td->td_locks;
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spincount = 0;
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@ -461,7 +462,7 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t
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critical_enter();
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*DPCPU_PTR(epoch_cb_count) += 1;
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er = epoch_currecord(epoch);
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ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback);
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ck_epoch_call(&er->er_write_record, cb, (ck_epoch_cb_t *)callback);
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critical_exit();
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return;
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boottime:
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@ -485,7 +486,7 @@ epoch_call_task(void *arg __unused)
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if (__predict_false((epoch = allepochs[i]) == NULL))
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continue;
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er = epoch_currecord(epoch);
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record = &er->er_record;
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record = &er->er_write_record;
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if ((npending = record->n_pending) == 0)
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continue;
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ck_epoch_poll_deferred(record, &cb_stack);
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@ -89,7 +89,8 @@ typedef struct epoch_thread {
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TAILQ_HEAD (epoch_tdlist, epoch_thread);
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typedef struct epoch_record {
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ck_epoch_record_t er_record;
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ck_epoch_record_t er_read_record;
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ck_epoch_record_t er_write_record;
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volatile struct epoch_tdlist er_tdlist;
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volatile uint32_t er_gen;
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uint32_t er_cpuid;
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@ -138,7 +139,7 @@ epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et)
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td->td_pre_epoch_prio = td->td_priority;
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er = epoch_currecord(epoch);
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TAILQ_INSERT_TAIL(&er->er_tdlist, etd, et_link);
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ck_epoch_begin(&er->er_record, (ck_epoch_section_t *)&etd->et_section);
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ck_epoch_begin(&er->er_read_record, (ck_epoch_section_t *)&etd->et_section);
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critical_exit_sa(td);
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}
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@ -155,7 +156,7 @@ epoch_enter(epoch_t epoch)
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td->td_epochnest++;
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critical_enter_sa(td);
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er = epoch_currecord(epoch);
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ck_epoch_begin(&er->er_record, NULL);
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ck_epoch_begin(&er->er_read_record, NULL);
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}
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static __inline void
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@ -183,7 +184,7 @@ epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et)
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etd->et_magic_post = 0;
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#endif
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etd->et_td = (void*)0xDEADBEEF;
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ck_epoch_end(&er->er_record,
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ck_epoch_end(&er->er_read_record,
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(ck_epoch_section_t *)&etd->et_section);
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TAILQ_REMOVE(&er->er_tdlist, etd, et_link);
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er->er_gen++;
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@ -203,7 +204,7 @@ epoch_exit(epoch_t epoch)
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MPASS(td->td_epochnest);
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td->td_epochnest--;
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er = epoch_currecord(epoch);
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ck_epoch_end(&er->er_record, NULL);
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ck_epoch_end(&er->er_read_record, NULL);
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critical_exit_sa(td);
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}
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#endif /* _KERNEL */
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