For compatibility KPI functions like if_addr_rlock() that used to have
mutexes but now are converted to epoch(9) use thread-private epoch_tracker. Embedding tracker into ifnet(9) or ifnet derived structures creates a non reentrable function, that will fail miserably if called simultaneously from two different contexts. A thread private tracker will provide a single tracker that would allow to call these functions safely. It doesn't allow nested call, but this is not expected from compatibility KPIs. Reviewed by: markj
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@ -272,6 +272,7 @@ thread_init(void *mem, int size, int flags)
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td->td_rlqe = NULL;
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EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
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umtx_thread_init(td);
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epoch_thread_init(td);
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td->td_kstack = 0;
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td->td_sel = NULL;
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return (0);
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@ -291,6 +292,7 @@ thread_fini(void *mem, int size)
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turnstile_free(td->td_turnstile);
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sleepq_free(td->td_sleepqueue);
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umtx_thread_fini(td);
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epoch_thread_fini(td);
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seltdfini(td);
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}
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@ -667,3 +667,17 @@ in_epoch(epoch_t epoch)
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{
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return (in_epoch_verbose(epoch, 0));
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}
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void
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epoch_thread_init(struct thread *td)
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{
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td->td_et = malloc(sizeof(struct epoch_tracker), M_EPOCH, M_WAITOK);
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}
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void
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epoch_thread_fini(struct thread *td)
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{
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free(td->td_et, M_EPOCH);
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}
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18
sys/net/if.c
18
sys/net/if.c
@ -1767,35 +1767,29 @@ if_data_copy(struct ifnet *ifp, struct if_data *ifd)
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void
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if_addr_rlock(struct ifnet *ifp)
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{
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MPASS(*(uint64_t *)&ifp->if_addr_et == 0);
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epoch_enter_preempt(net_epoch_preempt, &ifp->if_addr_et);
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epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
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}
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void
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if_addr_runlock(struct ifnet *ifp)
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{
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epoch_exit_preempt(net_epoch_preempt, &ifp->if_addr_et);
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#ifdef INVARIANTS
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bzero(&ifp->if_addr_et, sizeof(struct epoch_tracker));
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#endif
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epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
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}
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void
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if_maddr_rlock(if_t ifp)
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{
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MPASS(*(uint64_t *)&ifp->if_maddr_et == 0);
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epoch_enter_preempt(net_epoch_preempt, &ifp->if_maddr_et);
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epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
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}
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void
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if_maddr_runlock(if_t ifp)
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{
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epoch_exit_preempt(net_epoch_preempt, &ifp->if_maddr_et);
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#ifdef INVARIANTS
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bzero(&ifp->if_maddr_et, sizeof(struct epoch_tracker));
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#endif
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epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
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}
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/*
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@ -381,8 +381,6 @@ struct ifnet {
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*/
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struct netdump_methods *if_netdump_methods;
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struct epoch_context if_epoch_ctx;
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struct epoch_tracker if_addr_et;
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struct epoch_tracker if_maddr_et;
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/*
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* Spare fields to be added before branching a stable branch, so
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@ -82,5 +82,8 @@ void epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et);
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void epoch_enter(epoch_t epoch);
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void epoch_exit(epoch_t epoch);
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void epoch_thread_init(struct thread *);
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void epoch_thread_fini(struct thread *);
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#endif /* _KERNEL */
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#endif /* _SYS_EPOCH_H_ */
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@ -193,6 +193,7 @@ struct trapframe;
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struct turnstile;
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struct vm_map;
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struct vm_map_entry;
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struct epoch_tracker;
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/*
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* XXX: Does this belong in resource.h or resourcevar.h instead?
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@ -360,6 +361,7 @@ struct thread {
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int td_lastcpu; /* (t) Last cpu we were on. */
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int td_oncpu; /* (t) Which cpu we are on. */
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void *td_lkpi_task; /* LinuxKPI task struct pointer */
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struct epoch_tracker *td_et; /* (k) compat KPI spare tracker */
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int td_pmcpend;
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};
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