On Thu, Mar 25, 2021 at 8:39 AM Dmitry Vyukov <[email protected]> wrote: > > On Wed, Mar 24, 2021 at 10:40 AM Eric Dumazet <[email protected]> wrote: > > > > On Tue, Mar 23, 2021 at 7:49 AM Dmitry Vyukov <[email protected]> wrote: > > > > > > netdev_wait_allrefs() issues a warning if refcount does not drop to 0 > > > after 10 seconds. While 10 second wait generally should not happen > > > under normal workload in normal environment, it seems to fire falsely > > > very often during fuzzing and/or in qemu emulation (~10x slower). > > > At least it's not possible to understand if it's really a false > > > positive or not. Automated testing generally bumps all timeouts > > > to very high values to avoid flake failures. > > > Add net.core.netdev_unregister_timeout_secs sysctl to make > > > the timeout configurable for automated testing systems. > > > Lowering the timeout may also be useful for e.g. manual bisection. > > > The default value matches the current behavior. > > > > > > Signed-off-by: Dmitry Vyukov <[email protected]> > > > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877 > > > Cc: [email protected] > > > Cc: [email protected] > > > > > > --- > > > Changes since v1: > > > - use sysctl instead of a config > > > --- > > > > > }, > > > + { > > > + .procname = "netdev_unregister_timeout_secs", > > > + .data = &netdev_unregister_timeout_secs, > > > + .maxlen = sizeof(unsigned int), > > > + .mode = 0644, > > > + .proc_handler = proc_dointvec_minmax, > > > + .extra1 = SYSCTL_ZERO, > > > + .extra2 = &int_3600, > > > + }, > > > { } > > > }; > > > > > > > If we allow the sysctl to be 0, then we risk a flood of pr_emerg() > > (one per jiffy ?) > > My reasoning was that it's up to the user. Some spammy output on the > console for rare events is probably not the worst way how root can > misconfigure the kernel :) > It allows one to check (more or less) if we are reaching > unregister_netdevice with non-zero refcount, which may be useful for > some debugging maybe. > But I don't mind changing it to 1 (or 5) if you prefer. On syzbot we > only want to increase it. >
Yes, please use a lower limit of one to avoid spurious reports.
