In message <201811132258.wadmwctl063...@repo.freebsd.org>, Gleb
Smirnoff writes
:
> Author: glebius
> Date: Tue Nov 13 22:58:38 2018
> New Revision: 340413
> URL: https://svnweb.freebsd.org/changeset/base/340413
>
> Log:
> 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
>
> Modified:
> head/sys/kern/kern_thread.c
> head/sys/kern/subr_epoch.c
> head/sys/net/if.c
> head/sys/net/if_var.h
> head/sys/sys/epoch.h
> head/sys/sys/proc.h
>
> Modified: head/sys/kern/kern_thread.c
> =============================================================================
> =
> --- head/sys/kern/kern_thread.c Tue Nov 13 22:41:20 2018 (r34041
> 2)
> +++ head/sys/kern/kern_thread.c Tue Nov 13 22:58:38 2018 (r34041
> 3)
> @@ -272,6 +272,7 @@ thread_init(void *mem, int size, int flags)
> td->td_rlqe = NULL;
> EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
> umtx_thread_init(td);
> + epoch_thread_init(td);
> td->td_kstack = 0;
> td->td_sel = NULL;
> return (0);
> @@ -291,6 +292,7 @@ thread_fini(void *mem, int size)
> turnstile_free(td->td_turnstile);
> sleepq_free(td->td_sleepqueue);
> umtx_thread_fini(td);
> + epoch_thread_fini(td);
> seltdfini(td);
> }
>
>
> Modified: head/sys/kern/subr_epoch.c
> =============================================================================
> =
> --- head/sys/kern/subr_epoch.c Tue Nov 13 22:41:20 2018 (r34041
> 2)
> +++ head/sys/kern/subr_epoch.c Tue Nov 13 22:58:38 2018 (r34041
> 3)
> @@ -667,3 +667,17 @@ in_epoch(epoch_t epoch)
> {
> return (in_epoch_verbose(epoch, 0));
> }
> +
> +void
> +epoch_thread_init(struct thread *td)
> +{
> +
> + td->td_et = malloc(sizeof(struct epoch_tracker), M_EPOCH, M_WAITOK);
> +}
> +
> +void
> +epoch_thread_fini(struct thread *td)
> +{
> +
> + free(td->td_et, M_EPOCH);
> +}
>
> Modified: head/sys/net/if.c
> =============================================================================
> =
> --- head/sys/net/if.c Tue Nov 13 22:41:20 2018 (r340412)
> +++ head/sys/net/if.c Tue Nov 13 22:58:38 2018 (r340413)
> @@ -1767,35 +1767,29 @@ if_data_copy(struct ifnet *ifp, struct if_data *ifd)
> void
> if_addr_rlock(struct ifnet *ifp)
> {
> - MPASS(*(uint64_t *)&ifp->if_addr_et == 0);
> - epoch_enter_preempt(net_epoch_preempt, &ifp->if_addr_et);
> +
> + epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
> }
>
> void
> if_addr_runlock(struct ifnet *ifp)
> {
> - epoch_exit_preempt(net_epoch_preempt, &ifp->if_addr_et);
> -#ifdef INVARIANTS
> - bzero(&ifp->if_addr_et, sizeof(struct epoch_tracker));
> -#endif
> +
> + epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
> }
>
> void
> if_maddr_rlock(if_t ifp)
> {
>
> - MPASS(*(uint64_t *)&ifp->if_maddr_et == 0);
> - epoch_enter_preempt(net_epoch_preempt, &ifp->if_maddr_et);
> + epoch_enter_preempt(net_epoch_preempt, curthread->td_et);
Hi Gleb,
I was wrong. It's happening here, called from line 084 in if_sk.c.
~cy
> }
>
> void
> if_maddr_runlock(if_t ifp)
> {
>
> - epoch_exit_preempt(net_epoch_preempt, &ifp->if_maddr_et);
> -#ifdef INVARIANTS
> - bzero(&ifp->if_maddr_et, sizeof(struct epoch_tracker));
> -#endif
> + epoch_exit_preempt(net_epoch_preempt, curthread->td_et);
> }
>
> /*
>
> Modified: head/sys/net/if_var.h
> =============================================================================
> =
> --- head/sys/net/if_var.h Tue Nov 13 22:41:20 2018 (r340412)
> +++ head/sys/net/if_var.h Tue Nov 13 22:58:38 2018 (r340413)
> @@ -381,8 +381,6 @@ struct ifnet {
> */
> struct netdump_methods *if_netdump_methods;
> struct epoch_context if_epoch_ctx;
> - struct epoch_tracker if_addr_et;
> - struct epoch_tracker if_maddr_et;
>
> /*
> * Spare fields to be added before branching a stable branch, so
>
> Modified: head/sys/sys/epoch.h
> =============================================================================
> =
> --- head/sys/sys/epoch.h Tue Nov 13 22:41:20 2018 (r340412)
> +++ head/sys/sys/epoch.h Tue Nov 13 22:58:38 2018 (r340413)
> @@ -82,5 +82,8 @@ void epoch_exit_preempt(epoch_t epoch, epoch_tracker_t
> void epoch_enter(epoch_t epoch);
> void epoch_exit(epoch_t epoch);
>
> +void epoch_thread_init(struct thread *);
> +void epoch_thread_fini(struct thread *);
> +
> #endif /* _KERNEL */
> #endif /* _SYS_EPOCH_H_ */
>
> Modified: head/sys/sys/proc.h
> =============================================================================
> =
> --- head/sys/sys/proc.h Tue Nov 13 22:41:20 2018 (r340412)
> +++ head/sys/sys/proc.h Tue Nov 13 22:58:38 2018 (r340413)
> @@ -193,6 +193,7 @@ struct trapframe;
> struct turnstile;
> struct vm_map;
> struct vm_map_entry;
> +struct epoch_tracker;
>
> /*
> * XXX: Does this belong in resource.h or resourcevar.h instead?
> @@ -360,6 +361,7 @@ struct thread {
> int td_lastcpu; /* (t) Last cpu we were on. */
> int td_oncpu; /* (t) Which cpu we are on. */
> void *td_lkpi_task; /* LinuxKPI task struct pointer */
> + struct epoch_tracker *td_et; /* (k) compat KPI spare tracker */
> int td_pmcpend;
> };
>
>
--
Cheers,
Cy Schubert <cy.schub...@cschubert.com>
FreeBSD UNIX: <c...@freebsd.org> Web: http://www.FreeBSD.org
The need of the many outweighs the greed of the few.
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