Date: Tue, 28 Oct 2025 21:23:40 GMT From: Colin Percival <cperciva@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 8376d05279ee - releng/15.0 - x86: Reduce amount of time the MCA lock is held while emitting records Message-ID: <202510282123.59SLNeQM075618@gitrepo.freebsd.org>
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The branch releng/15.0 has been updated by cperciva: URL: https://cgit.FreeBSD.org/src/commit/?id=8376d05279ee78e39f8face7b307772c8c306fa7 commit 8376d05279ee78e39f8face7b307772c8c306fa7 Author: Jonathan T. Looney <jtl@FreeBSD.org> AuthorDate: 2025-10-06 15:07:33 +0000 Commit: Colin Percival <cperciva@FreeBSD.org> CommitDate: 2025-10-28 21:23:05 +0000 x86: Reduce amount of time the MCA lock is held while emitting records The MCA spin lock is acquired in the hardware interrupt context to record MCA messages. It is also acquired by a task handler to emit those messages. Reduce the amount of time the task handler holds the lock to reduce the maximum amount of time the hardware interrupt handler may need to spin on the lock. Approved by: re (cperciva) Reviewed by: glebius, markj Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D52938 (cherry picked from commit e770e32aa3a017b35fcf24e7c6f14fc2a209bad5) (cherry picked from commit d83dee356dce39b0282bce1f8d7d1ba976995d57) --- sys/x86/x86/mca.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/sys/x86/x86/mca.c b/sys/x86/x86/mca.c index e43c88b3a27b..7ee22895e0a7 100644 --- a/sys/x86/x86/mca.c +++ b/sys/x86/x86/mca.c @@ -796,9 +796,9 @@ mca_record_entry(enum scan_mode mode, const struct mca_record *record) mtx_lock_spin(&mca_lock); rec = STAILQ_FIRST(&mca_freelist); if (rec == NULL) { + mtx_unlock_spin(&mca_lock); printf("MCA: Unable to allocate space for an event.\n"); mca_log(record); - mtx_unlock_spin(&mca_lock); return; } STAILQ_REMOVE_HEAD(&mca_freelist, link); @@ -1017,6 +1017,7 @@ static void mca_process_records(enum scan_mode mode) { struct mca_internal *mca; + STAILQ_HEAD(, mca_internal) tmplist; /* * If in an interrupt context, defer the post-scan activities to a @@ -1028,10 +1029,21 @@ mca_process_records(enum scan_mode mode) return; } + /* + * Copy the pending list to the stack so we can drop the spin lock + * while we are emitting logs. + */ + STAILQ_INIT(&tmplist); mtx_lock_spin(&mca_lock); - while ((mca = STAILQ_FIRST(&mca_pending)) != NULL) { - STAILQ_REMOVE_HEAD(&mca_pending, link); + STAILQ_SWAP(&mca_pending, &tmplist, mca_internal); + mtx_unlock_spin(&mca_lock); + + STAILQ_FOREACH(mca, &tmplist, link) mca_log(&mca->rec); + + mtx_lock_spin(&mca_lock); + while ((mca = STAILQ_FIRST(&tmplist)) != NULL) { + STAILQ_REMOVE_HEAD(&tmplist, link); mca_store_record(mca); } mtx_unlock_spin(&mca_lock);home | help
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