Date: Tue, 9 May 2023 16:48:54 GMT From: "Jonathan T. Looney" <jtl@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 8a16fb47303e - main - locks: fix two potential overflows in the lock delay code Message-ID: <202305091648.349GmsOs046288@gitrepo.freebsd.org>
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The branch main has been updated by jtl: URL: https://cgit.FreeBSD.org/src/commit/?id=8a16fb47303ef4bfc773b52a920e0b223f8e9c20 commit 8a16fb47303ef4bfc773b52a920e0b223f8e9c20 Author: Jonathan T. Looney <jtl@FreeBSD.org> AuthorDate: 2023-05-09 16:20:49 +0000 Commit: Jonathan T. Looney <jtl@FreeBSD.org> CommitDate: 2023-05-09 16:20:49 +0000 locks: fix two potential overflows in the lock delay code With large numbers of CPUs, the calculation of the maximum lock delay could overflow, leading to an unexpectedly low delay. In fact, the maximum delay would calculate to 0 on systems with between 128 and 255 cores (inclusive). Also, when calculating the new delay in lock_delay(), the delay would overflow if the old delay was >= 32,768. This commit fixes these two overflows. It also updates the maximum delay from 32,678 to SHRT_MAX. Reviewed by: gallatin, jhb, mjg Fixes: 6b8dd26e7c5f ("locks: convert delay times to u_short") MFC after: 2 weeks Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D39372 --- sys/kern/subr_lock.c | 8 +++----- sys/sys/lock.h | 2 +- 2 files changed, 4 insertions(+), 6 deletions(-) diff --git a/sys/kern/subr_lock.c b/sys/kern/subr_lock.c index 1061ed5f5d03..05ce8b73b086 100644 --- a/sys/kern/subr_lock.c +++ b/sys/kern/subr_lock.c @@ -121,14 +121,14 @@ void lock_delay(struct lock_delay_arg *la) { struct lock_delay_config *lc = la->config; - u_short i; + u_int i; for (i = la->delay; i > 0; i--) cpu_spinwait(); la->spin_cnt += la->delay; la->delay <<= 1; - if (__predict_false(la->delay > lc->max)) + if (__predict_false(la->delay > (u_int)lc->max)) la->delay = lc->max; } @@ -148,9 +148,7 @@ lock_delay_default_init(struct lock_delay_config *lc) { lc->base = 1; - lc->max = lock_roundup_2(mp_ncpus) * 256; - if (lc->max > 32678) - lc->max = 32678; + lc->max = min(lock_roundup_2(mp_ncpus) * 256, SHRT_MAX); } struct lock_delay_config __read_frequently locks_delay; diff --git a/sys/sys/lock.h b/sys/sys/lock.h index 4031f20946c0..ce66a8ffebba 100644 --- a/sys/sys/lock.h +++ b/sys/sys/lock.h @@ -182,7 +182,7 @@ extern u_short locks_delay_loops; struct lock_delay_arg { struct lock_delay_config *config; - u_short delay; + u_int delay; u_int spin_cnt; };
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