kernel/linux.git/include/linux/sched/smt.h, branch v7.2-rc6

sched: Simplify ifdeffery around cpu_smt_mask

2026-05-19T10:17:37+00:00

Now, that cpu_smt_mask is defined as cpumask_of(cpu) for CONFIG_SCHED_SMT=n, it is possible to get rid of the ifdeffery. Effectively, - This makes sched_smt_present is defined always - cpumask_weight(cpumask_of(cpu)) == 1. So sched_smt_present_inc/dec will never enable the sched_smt_present. Which is expected. - Paths that were compile-time eliminated become runtime guarded using static keys. - Defines set_idle_cores, test_idle_cores, etc which could likely benefit the CONFIG_SCHED_SMT=n systems to use the same optimizations within the LLC at wakeups. - This will expose sched_smt_present symbol for CONFIG_SCHED_SMT=n. Likely not a concern. - There is a bloat of code CONFIG_SCHED_SMT=n. (NR_CPUS=2048) add/remove: 24/18 grow/shrink: 26/28 up/down: 6396/-3188 (3208) Total: Before=30629880, After=30633088, chg +0.01% - No code bloat for CONFIG_SCHED_SMT=y, which is expected. - Add comments around stop_core_cpuslocked on why ifdefs are not removed. - This leaves the remaining uses of CONFIG_SCHED_SMT mainly for topology building bits which has a policy based decision. Signed-off-by: Shrikanth Hegde Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Phil Auld Reviewed-by: Valentin Schneider Acked-by: Tejun Heo Tested-by: K Prateek Nayak Link: https://patch.msgid.link/20260515172456.542799-3-sshegde@linux.ibm.com

sched/smt: Always inline sched_smt_active()

2025-04-01T07:07:13+00:00

sched_smt_active() can be called from noinstr code, so it should always be inlined. The CONFIG_SCHED_SMT version already has __always_inline. Do the same for its !CONFIG_SCHED_SMT counterpart. Fixes the following warning: vmlinux.o: error: objtool: intel_idle_ibrs+0x13: call to sched_smt_active() leaves .noinstr.text section Fixes: 321a874a7ef8 ("sched/smt: Expose sched_smt_present static key") Reported-by: kernel test robot Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/1d03907b0a247cf7fb5c1d518de378864f603060.1743481539.git.jpoimboe@kernel.org Closes: https://lore.kernel.org/r/202503311434.lyw2Tveh-lkp@intel.com/

sched/headers: Standardize the header guard #endif

2023-09-21T09:28:48+00:00

Signed-off-by: Ingo Molnar

x86/speculation: Rework SMT state change

2018-11-28T10:57:07+00:00

arch_smt_update() is only called when the sysfs SMT control knob is changed. This means that when SMT is enabled in the sysfs control knob the system is considered to have SMT active even if all siblings are offline. To allow finegrained control of the speculation mitigations, the actual SMT state is more interesting than the fact that siblings could be enabled. Rework the code, so arch_smt_update() is invoked from each individual CPU hotplug function, and simplify the update function while at it. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185004.521974984@linutronix.de

sched/smt: Expose sched_smt_present static key

2018-11-28T10:57:07+00:00

Make the scheduler's 'sched_smt_present' static key globaly available, so it can be used in the x86 speculation control code. Provide a query function and a stub for the CONFIG_SMP=n case. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185004.430168326@linutronix.de