From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- Documentation/admin-guide/sysctl/crypto.rst | 83 +++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 Documentation/admin-guide/sysctl/crypto.rst (limited to 'Documentation/admin-guide/sysctl/crypto.rst') diff --git a/Documentation/admin-guide/sysctl/crypto.rst b/Documentation/admin-guide/sysctl/crypto.rst new file mode 100644 index 000000000..9a1bd5328 --- /dev/null +++ b/Documentation/admin-guide/sysctl/crypto.rst @@ -0,0 +1,83 @@ +================= +/proc/sys/crypto/ +================= + +These files show up in ``/proc/sys/crypto/``, depending on the +kernel configuration: + +.. contents:: :local: + +.. _af_alg_restrict: + +af_alg_restrict +=============== + +Controls the level of restriction of AF_ALG. + +AF_ALG is a deprecated and rarely-used userspace interface that is a +frequent source of vulnerabilities. It also unnecessarily exposes a +large number of kernel implementation details. For more information +about AF_ALG, see :ref:`Documentation/crypto/userspace-if.rst +`. + +Starting in Linux v7.3, AF_ALG supports only a limited set of +algorithms by default. This sysctl allows the system administrator to +remove this restriction when needed for compatibility reasons, or to +go further and disable AF_ALG entirely. The default value is 1. + +=== ================================================================== +0 AF_ALG is unrestricted. + +1 AF_ALG is supported with a limited list of algorithms. The list + is designed for compatibility with known users such as iwd and + bluez that haven't yet been fixed to use userspace crypto code. + + Specifically, there is an allowlist for unprivileged processes + and a somewhat longer allowlist for processes that hold + CAP_SYS_ADMIN or CAP_NET_ADMIN in the initial user namespace. + + Attempts to bind() an AF_ALG socket with a disallowed algorithm + fail with ENOENT. + +2 AF_ALG is completely disabled. Attempts to create an AF_ALG + socket fail with EAFNOSUPPORT. +=== ================================================================== + +fips_enabled +============ + +Read-only flag that indicates whether FIPS mode is enabled. + +- ``0``: FIPS mode is disabled (default). +- ``1``: FIPS mode is enabled. + +This value is set at boot time via the ``fips=1`` kernel command line +parameter. When enabled, the cryptographic API will restrict the use +of certain algorithms and perform self-tests to ensure compliance with +FIPS (Federal Information Processing Standards) requirements, such as +FIPS 140-2 and the newer FIPS 140-3, depending on the kernel +configuration and the module in use. + +fips_name +========= + +Read-only file that contains the name of the FIPS module currently in use. +The value is typically configured via the ``CONFIG_CRYPTO_FIPS_NAME`` +kernel configuration option. + +fips_version +============ + +Read-only file that contains the version string of the FIPS module. +If ``CONFIG_CRYPTO_FIPS_CUSTOM_VERSION`` is set, it uses the value from +``CONFIG_CRYPTO_FIPS_VERSION``. Otherwise, it defaults to the kernel +release version (``UTS_RELEASE``). + +Copyright (c) 2026, Shubham Chakraborty + +For general info and legal blurb, please look in +Documentation/admin-guide/sysctl/index.rst. + +.. See scripts/check-sysctl-docs to keep this up to date: +.. scripts/check-sysctl-docs -vtable="crypto" \ +.. $(git grep -l register_sysctl_) -- cgit v1.3.1