Date: Fri, 4 Dec 2020 02:18:40 +0000 (UTC) From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r368321 - stable/12/sys/kern Message-ID: <202012040218.0B42Ietn054934@repo.freebsd.org>
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Author: kevans Date: Fri Dec 4 02:18:40 2020 New Revision: 368321 URL: https://svnweb.freebsd.org/changeset/base/368321 Log: MFC r368116: kern: cpuset: drop the lock to allocate domainsets Restructure the loop a little bit to make it a little more clear how it really operates: we never allocate any domains at the beginning of the first iteration, and it will run until we've satisfied the amount we need or we encounter an error. The lock is now taken outside of the loop to make stuff inside the loop easier to evaluate w.r.t. locking. This fixes it to not try and allocate any domains for the freelist under the spinlock, which would have happened before if we needed any new domains. Modified: stable/12/sys/kern/kern_cpuset.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/kern_cpuset.c ============================================================================== --- stable/12/sys/kern/kern_cpuset.c Fri Dec 4 01:11:09 2020 (r368320) +++ stable/12/sys/kern/kern_cpuset.c Fri Dec 4 02:18:40 2020 (r368321) @@ -784,14 +784,11 @@ cpuset_modify_domain(struct cpuset *set, struct domain return (EPERM); domainset_freelist_init(&domains, 0); domain = domainset_create(domain); - ndomains = needed = 0; - do { - if (ndomains < needed) { - domainset_freelist_add(&domains, needed - ndomains); - ndomains = needed; - } + ndomains = 0; + + mtx_lock_spin(&cpuset_lock); + for (;;) { root = cpuset_getroot(set); - mtx_lock_spin(&cpuset_lock); dset = root->cs_domain; /* * Verify that we have access to this set of domains. @@ -816,7 +813,15 @@ cpuset_modify_domain(struct cpuset *set, struct domain &needed, 0); if (error) goto out; - } while (ndomains < needed); + if (ndomains >= needed) + break; + + /* Dropping the lock; we'll need to re-evaluate again. */ + mtx_unlock_spin(&cpuset_lock); + domainset_freelist_add(&domains, needed - ndomains); + ndomains = needed; + mtx_lock_spin(&cpuset_lock); + } dset = set->cs_domain; cpuset_update_domain(set, domain, dset, &domains); out:
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