Date: Tue, 14 Mar 2017 14:57:06 -0700 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Kristof Provost <kp@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r315136 - head/sys/netpfil/pf Message-ID: <20170314215706.GB1072@FreeBSD.org> In-Reply-To: <201703120542.v2C5gvM4075391@repo.freebsd.org> References: <201703120542.v2C5gvM4075391@repo.freebsd.org>
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Kristof,
On Sun, Mar 12, 2017 at 05:42:57AM +0000, Kristof Provost wrote:
K> Log:
K> pf: Fix incorrect rw_sleep() in pf_unload()
K>
K> When we unload we don't hold the pf_rules_lock, so we cannot call rw_sleep()
K> with it, because it would release a lock we do not hold. There's no need for the
K> lock either, so we can just tsleep().
K>
K> While here also make the same change in pf_purge_thread(), because it explicitly
K> takes the lock before rw_sleep() and then immediately releases it afterwards.
The correct change would to be grab lock in pf_unload(), exactly as pf_purge_thread()
does. With your change you introduces a possible infinite sleep due to race, since
there is no timeout and no lock.
No... Actually both cases should PF_RULES_WLOCK(), and read/write the pf_end_threads
variable under this lock. And use rw_sleep.
K> Modified:
K> head/sys/netpfil/pf/pf.c
K> head/sys/netpfil/pf/pf_ioctl.c
K>
K> Modified: head/sys/netpfil/pf/pf.c
K> ==============================================================================
K> --- head/sys/netpfil/pf/pf.c Sun Mar 12 05:36:31 2017 (r315135)
K> +++ head/sys/netpfil/pf/pf.c Sun Mar 12 05:42:57 2017 (r315136)
K> @@ -1429,9 +1429,7 @@ pf_purge_thread(void *unused __unused)
K> u_int idx = 0;
K>
K> for (;;) {
K> - PF_RULES_RLOCK();
K> - rw_sleep(pf_purge_thread, &pf_rules_lock, 0, "pftm", hz / 10);
K> - PF_RULES_RUNLOCK();
K> + tsleep(pf_purge_thread, 0, "pftm", hz / 10);
K>
K> VNET_LIST_RLOCK();
K> VNET_FOREACH(vnet_iter) {
K>
K> Modified: head/sys/netpfil/pf/pf_ioctl.c
K> ==============================================================================
K> --- head/sys/netpfil/pf/pf_ioctl.c Sun Mar 12 05:36:31 2017 (r315135)
K> +++ head/sys/netpfil/pf/pf_ioctl.c Sun Mar 12 05:42:57 2017 (r315136)
K> @@ -3791,7 +3791,7 @@ pf_unload(void)
K> pf_end_threads = 1;
K> while (pf_end_threads < 2) {
K> wakeup_one(pf_purge_thread);
K> - rw_sleep(pf_purge_thread, &pf_rules_lock, 0, "pftmo", 0);
K> + tsleep(pf_purge_thread, 0, "pftmo", 0);
K> }
K>
K> if (pf_dev != NULL)
K> _______________________________________________
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--
Totus tuus, Glebius.
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