kernel/linux.git/arch/x86/include/asm/preempt.h, branch v6.2

x86/percpu: Move preempt_count next to current_task

2022-10-17T14:41:04+00:00

Add preempt_count to pcpu_hot, since it is once of the most used per-cpu variables. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220915111145.284170644@infradead.org

sched/preempt: Refactor sched_dynamic_update()

2022-02-19T10:11:07+00:00

Currently sched_dynamic_update needs to open-code the enabled/disabled function names for each preemption model it supports, when in practice this is a boolean enabled/disabled state for each function. Make this clearer and avoid repetition by defining the enabled/disabled states at the function definition, and using helper macros to perform the static_call_update(). Where x86 currently overrides the enabled function, it is made to provide both the enabled and disabled states for consistency, with defaults provided by the core code otherwise. In subsequent patches this will allow us to support PREEMPT_DYNAMIC without static calls. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Acked-by: Ard Biesheuvel Acked-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20220214165216.2231574-3-mark.rutland@arm.com

sched/core: Initialize the idle task with preemption disabled

2021-05-12T11:01:45+00:00

As pointed out by commit de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread") init_idle() can and will be invoked more than once on the same idle task. At boot time, it is invoked for the boot CPU thread by sched_init(). Then smp_init() creates the threads for all the secondary CPUs and invokes init_idle() on them. As the hotplug machinery brings the secondaries to life, it will issue calls to idle_thread_get(), which itself invokes init_idle() yet again. In this case it's invoked twice more per secondary: at _cpu_up(), and at bringup_cpu(). Given smp_init() already initializes the idle tasks for all *possible* CPUs, no further initialization should be required. Now, removing init_idle() from idle_thread_get() exposes some interesting expectations with regards to the idle task's preempt_count: the secondary startup always issues a preempt_disable(), requiring some reset of the preempt count to 0 between hot-unplug and hotplug, which is currently served by idle_thread_get() -> idle_init(). Given the idle task is supposed to have preemption disabled once and never see it re-enabled, it seems that what we actually want is to initialize its preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove init_idle() from idle_thread_get(). Secondary startups were patched via coccinelle: @begone@ @@ -preempt_disable(); ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); Signed-off-by: Valentin Schneider Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com

sched,x86: Allow !PREEMPT_DYNAMIC

2021-02-17T13:12:43+00:00

Allow building x86 with PREEMPT_DYNAMIC=n, this is needed for PREEMPT_RT as it makes no sense to not have full preemption on PREEMPT_RT. Fixes: 8c98e8cf723c ("preempt/dynamic: Provide preempt_schedule[_notrace]() static calls") Reported-by: Mike Galbraith Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Tested-by: Mike Galbraith Link: https://lkml.kernel.org/r/YCK1+JyFNxQnWeXK@hirez.programming.kicks-ass.net

sched: Harden PREEMPT_DYNAMIC

2021-02-17T13:12:42+00:00

Use the new EXPORT_STATIC_CALL_TRAMP() / static_call_mod() to unexport the static_call_key for the PREEMPT_DYNAMIC calls such that modules can no longer update these calls. Having modules change/hi-jack the preemption calls would be horrible. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar

preempt/dynamic: Provide preempt_schedule[_notrace]() static calls

2021-02-17T13:12:42+00:00

Provide static calls to control preempt_schedule[_notrace]() (called in CONFIG_PREEMPT) so that we can override their behaviour when preempt= is overriden. Since the default behaviour is full preemption, both their calls are initialized to the arch provided wrapper, if any. [fweisbec: only define static calls when PREEMPT_DYNAMIC, make it less dependent on x86 with __preempt_schedule_func] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20210118141223.123667-7-frederic@kernel.org

x86/entry: Rename ___preempt_schedule

2020-03-21T15:03:53+00:00

Because moar '_' isn't always moar readable. git grep -l "___preempt_schedule$_notrace$*" | while read file; do sed -ie 's/___preempt_schedule$_notrace$*/preempt_schedule\1_thunk/g' $file; done Reported-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Acked-by: Will Deacon Link: https://lkml.kernel.org/r/20200320115858.995685950@infradead.org

x86: Use CONFIG_PREEMPTION

2019-07-31T17:03:35+00:00

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Switch the entry code, preempt and kprobes conditionals over to CONFIG_PREEMPTION. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Paolo Bonzini Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20190726212124.608488448@linutronix.de Signed-off-by: Ingo Molnar

preempt: Move PREEMPT_NEED_RESCHED definition into arch code

2018-12-07T12:35:46+00:00

PREEMPT_NEED_RESCHED is never used directly, so move it into the arch code where it can potentially be implemented using either a different bit in the preempt count or as an entirely separate entity. Cc: Robert Love Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Martin Schwidefsky Acked-by: Peter Zijlstra (Intel) Signed-off-by: Will Deacon

x86/asm: 'Simplify' GEN_*_RMWcc() macros

2018-10-16T15:33:54+00:00

Currently the GEN_*_RMWcc() macros include a return statement, which pretty much mandates we directly wrap them in a (inline) function. Macros with return statements are tricky and, as per the above, limit use, so remove the return statement and make them statement-expressions. This allows them to be used more widely. Also, shuffle the arguments a bit. Place the @cc argument as 3rd, this makes it consistent between UNARY and BINARY, but more importantly, it makes the @arg0 argument last. Since the @arg0 argument is now last, we can do CPP trickery and make it an optional argument, simplifying the users; 17 out of 18 occurences do not need this argument. Finally, change to asm symbolic names, instead of the numeric ordering of operands, which allows us to get rid of __BINARY_RMWcc_ARG and get cleaner code overall. Signed-off-by: Peter Zijlstra (Intel) Cc: JBeulich@suse.com Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bp@alien8.de Cc: hpa@linux.intel.com Link: https://lkml.kernel.org/r/20181003130957.108960094@infradead.org Signed-off-by: Ingo Molnar