diff options
author | Valentin Schneider <valentin.schneider@arm.com> | 2021-05-12 10:46:36 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2021-05-12 13:01:45 +0200 |
commit | f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 (patch) | |
tree | 591f2066a33afd8327ce2476705c105a65979f18 /arch | |
parent | 9f26990074931bbf797373e53104216059b300b1 (diff) | |
download | linux-stable-f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674.tar.gz linux-stable-f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674.tar.bz2 linux-stable-f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674.zip |
sched/core: Initialize the idle task with preemption disabled
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 <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
Diffstat (limited to 'arch')
-rw-r--r-- | arch/alpha/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/arc/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/arm/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/arm64/include/asm/preempt.h | 2 | ||||
-rw-r--r-- | arch/arm64/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/csky/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/ia64/kernel/smpboot.c | 1 | ||||
-rw-r--r-- | arch/mips/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/openrisc/kernel/smp.c | 2 | ||||
-rw-r--r-- | arch/parisc/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/powerpc/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/riscv/kernel/smpboot.c | 1 | ||||
-rw-r--r-- | arch/s390/include/asm/preempt.h | 4 | ||||
-rw-r--r-- | arch/s390/kernel/smp.c | 1 | ||||
-rw-r--r-- | arch/sh/kernel/smp.c | 2 | ||||
-rw-r--r-- | arch/sparc/kernel/smp_32.c | 1 | ||||
-rw-r--r-- | arch/sparc/kernel/smp_64.c | 3 | ||||
-rw-r--r-- | arch/x86/include/asm/preempt.h | 2 | ||||
-rw-r--r-- | arch/x86/kernel/smpboot.c | 1 | ||||
-rw-r--r-- | arch/xtensa/kernel/smp.c | 1 |
20 files changed, 4 insertions, 25 deletions
diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c index f4dd9f3f3001..4b2575f936d4 100644 --- a/arch/alpha/kernel/smp.c +++ b/arch/alpha/kernel/smp.c @@ -166,7 +166,6 @@ smp_callin(void) DBGS(("smp_callin: commencing CPU %d current %p active_mm %p\n", cpuid, current, current->active_mm)); - preempt_disable(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); } diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c index 52906d314537..db0e104d6835 100644 --- a/arch/arc/kernel/smp.c +++ b/arch/arc/kernel/smp.c @@ -189,7 +189,6 @@ void start_kernel_secondary(void) pr_info("## CPU%u LIVE ##: Executing Code...\n", cpu); local_irq_enable(); - preempt_disable(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); } diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 74679240a9d8..c7bb168b0d97 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -432,7 +432,6 @@ asmlinkage void secondary_start_kernel(void) #endif pr_debug("CPU%u: Booted secondary processor\n", cpu); - preempt_disable(); trace_hardirqs_off(); /* diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index 80e946b2abee..e83f0982b99c 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -23,7 +23,7 @@ static inline void preempt_count_set(u64 pc) } while (0) #define init_idle_preempt_count(p, cpu) do { \ - task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \ + task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \ } while (0) static inline void set_preempt_need_resched(void) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index dcd7041b2b07..6671000a8b7d 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -224,7 +224,6 @@ asmlinkage notrace void secondary_start_kernel(void) init_gic_priority_masking(); rcu_cpu_starting(cpu); - preempt_disable(); trace_hardirqs_off(); /* diff --git a/arch/csky/kernel/smp.c b/arch/csky/kernel/smp.c index 0f9f5eef9338..e2993539af8e 100644 --- a/arch/csky/kernel/smp.c +++ b/arch/csky/kernel/smp.c @@ -281,7 +281,6 @@ void csky_start_secondary(void) pr_info("CPU%u Online: %s...\n", cpu, __func__); local_irq_enable(); - preempt_disable(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); } diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c index 49b488580939..d10f780c13b9 100644 --- a/arch/ia64/kernel/smpboot.c +++ b/arch/ia64/kernel/smpboot.c @@ -441,7 +441,6 @@ start_secondary (void *unused) #endif efi_map_pal_code(); cpu_init(); - preempt_disable(); smp_callin(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index ef86fbad8546..d542fb7af3ba 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -348,7 +348,6 @@ asmlinkage void start_secondary(void) */ calibrate_delay(); - preempt_disable(); cpu = smp_processor_id(); cpu_data[cpu].udelay_val = loops_per_jiffy; diff --git a/arch/openrisc/kernel/smp.c b/arch/openrisc/kernel/smp.c index 48e1092a64de..415e209732a3 100644 --- a/arch/openrisc/kernel/smp.c +++ b/arch/openrisc/kernel/smp.c @@ -145,8 +145,6 @@ asmlinkage __init void secondary_start_kernel(void) set_cpu_online(cpu, true); local_irq_enable(); - - preempt_disable(); /* * OK, it's off to the idle thread for us */ diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c index 10227f667c8a..1405b603b91b 100644 --- a/arch/parisc/kernel/smp.c +++ b/arch/parisc/kernel/smp.c @@ -302,7 +302,6 @@ void __init smp_callin(unsigned long pdce_proc) #endif smp_cpu_init(slave_id); - preempt_disable(); flush_cache_all_local(); /* start with known state */ flush_tlb_all_local(NULL); diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 2e05c783440a..6c6e4d934d86 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1547,7 +1547,6 @@ void start_secondary(void *unused) smp_store_cpu_info(cpu); set_dec(tb_ticks_per_jiffy); rcu_cpu_starting(cpu); - preempt_disable(); cpu_callin_map[cpu] = 1; if (smp_ops->setup_cpu) diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c index 9a408e2942ac..bd82375db51a 100644 --- a/arch/riscv/kernel/smpboot.c +++ b/arch/riscv/kernel/smpboot.c @@ -180,7 +180,6 @@ asmlinkage __visible void smp_callin(void) * Disable preemption before enabling interrupts, so we don't try to * schedule a CPU that hasn't actually started yet. */ - preempt_disable(); local_irq_enable(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); } diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h index b49e0492842c..23ff51be7e29 100644 --- a/arch/s390/include/asm/preempt.h +++ b/arch/s390/include/asm/preempt.h @@ -32,7 +32,7 @@ static inline void preempt_count_set(int pc) #define init_task_preempt_count(p) do { } while (0) #define init_idle_preempt_count(p, cpu) do { \ - S390_lowcore.preempt_count = PREEMPT_ENABLED; \ + S390_lowcore.preempt_count = PREEMPT_DISABLED; \ } while (0) static inline void set_preempt_need_resched(void) @@ -91,7 +91,7 @@ static inline void preempt_count_set(int pc) #define init_task_preempt_count(p) do { } while (0) #define init_idle_preempt_count(p, cpu) do { \ - S390_lowcore.preempt_count = PREEMPT_ENABLED; \ + S390_lowcore.preempt_count = PREEMPT_DISABLED; \ } while (0) static inline void set_preempt_need_resched(void) diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 2fec2b80d35d..111909aeb8d2 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -878,7 +878,6 @@ static void smp_init_secondary(void) restore_access_regs(S390_lowcore.access_regs_save_area); cpu_init(); rcu_cpu_starting(cpu); - preempt_disable(); init_cpu_timer(); vtime_init(); vdso_getcpu_init(); diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c index 372acdc9033e..65924d9ec245 100644 --- a/arch/sh/kernel/smp.c +++ b/arch/sh/kernel/smp.c @@ -186,8 +186,6 @@ asmlinkage void start_secondary(void) per_cpu_trap_init(); - preempt_disable(); - notify_cpu_starting(cpu); local_irq_enable(); diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c index 50c127ab46d5..22b148e5a5f8 100644 --- a/arch/sparc/kernel/smp_32.c +++ b/arch/sparc/kernel/smp_32.c @@ -348,7 +348,6 @@ static void sparc_start_secondary(void *arg) */ arch_cpu_pre_starting(arg); - preempt_disable(); cpu = smp_processor_id(); notify_cpu_starting(cpu); diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c index e38d8bf454e8..ae5faa1d989d 100644 --- a/arch/sparc/kernel/smp_64.c +++ b/arch/sparc/kernel/smp_64.c @@ -138,9 +138,6 @@ void smp_callin(void) set_cpu_online(cpuid, true); - /* idle thread is expected to have preempt disabled */ - preempt_disable(); - local_irq_enable(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index f8cb8af4de5c..fe5efbcba824 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -44,7 +44,7 @@ static __always_inline void preempt_count_set(int pc) #define init_task_preempt_count(p) do { } while (0) #define init_idle_preempt_count(p, cpu) do { \ - per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \ + per_cpu(__preempt_count, (cpu)) = PREEMPT_DISABLED; \ } while (0) /* diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 0ad5214f598a..0936f5ba3222 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -236,7 +236,6 @@ static void notrace start_secondary(void *unused) cpu_init(); rcu_cpu_starting(raw_smp_processor_id()); x86_cpuinit.early_percpu_clock_init(); - preempt_disable(); smp_callin(); enable_start_cpu0 = 0; diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index cd85a7a2722b..1254da07ead1 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -145,7 +145,6 @@ void secondary_start_kernel(void) cpumask_set_cpu(cpu, mm_cpumask(mm)); enter_lazy_tlb(mm, current); - preempt_disable(); trace_hardirqs_off(); calibrate_delay(); |