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f1a0a376ca
linux-next/arch/alpha/kernel
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Valentin Schneider f1a0a376ca sched/core: Initialize the idle task with preemption disabled 
As pointed out by commit

  de9b8f5dcb ("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
2021-05-12 13:01:45 +02:00
..
syscalls Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com> 2021-05-01 18:50:44 -07:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
asm-offsets.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
audit.c alpha: Enable system-call auditing support. 2014-01-31 09:21:55 -08:00
binfmt_loader.c exec: Remove recursion from search_binary_handler 2020-05-21 10:16:57 -05:00
bugs.c alpha: Implement CPU vulnerabilities sysfs functions. 2018-04-07 15:04:04 -07:00
console.c vgacon: Set VGA struct resource types 2017-12-18 23:07:43 -06:00
core_apecs.c memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
core_cia.c treewide: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
core_irongate.c mm: remove unneeded includes of <asm/pgalloc.h> 2020-08-07 11:33:26 -07:00
core_lca.c memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
core_marvel.c iomap: constify ioreadX() iomem argument (as in generic implementation) 2020-08-14 19:56:57 -07:00
core_mcpcia.c memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
core_polaris.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
core_t2.c memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
core_titan.c mm: remove unneeded includes of <asm/pgalloc.h> 2020-08-07 11:33:26 -07:00
core_tsunami.c memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
core_wildfire.c alpha: fix spelling mistake QSD_PORT_ACTUVE -> QSD_PORT_ACTIVE 2018-12-21 11:57:57 -05:00
entry.S alpha: add support for TIF_NOTIFY_SIGNAL 2020-12-12 09:16:34 -07:00
err_common.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
err_ev6.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
err_ev7.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
err_impl.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
err_marvel.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
err_titan.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
es1888.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
gct.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
io.c iomap: constify ioreadX() iomem argument (as in generic implementation) 2020-08-14 19:56:57 -07:00
irq_alpha.c alpha: Replace setup_irq() by request_irq() 2020-03-29 21:03:41 +02:00
irq_i8259.c alpha: Replace setup_irq() by request_irq() 2020-03-29 21:03:41 +02:00
irq_impl.h alpha: Replace setup_irq() by request_irq() 2020-03-29 21:03:41 +02:00
irq_pyxis.c alpha: Replace setup_irq() by request_irq() 2020-03-29 21:03:41 +02:00
irq_srm.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
machvec_impl.h mm: remove unneeded includes of <asm/pgalloc.h> 2020-08-07 11:33:26 -07:00
Makefile alpha: Implement CPU vulnerabilities sysfs functions. 2018-04-07 15:04:04 -07:00
module.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
osf_sys.c alpha: remove unneeded semicolon in osf_sys.c 2020-06-12 17:43:17 -07:00
pc873xx.c alpha: eliminate old-style function definitions 2021-05-06 19:24:11 -07:00
pc873xx.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pci_impl.h alpha: fix reboot on Avanti platform 2018-01-20 17:01:10 -08:00
pci_iommu.c dma-mapping: split <linux/dma-mapping.h> 2020-10-06 07:07:03 +02:00
pci-noop.c treewide: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
pci-sysfs.c PCI: Add PCI_STD_NUM_BARS for the number of standard BARs 2019-10-14 10:22:26 -05:00
pci.c treewide: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
perf_event.c alpha: Use pr_warn instead of pr_warning 2019-10-18 10:26:32 +02:00
process.c arch: setup PF_IO_WORKER threads like PF_KTHREAD 2021-02-21 17:25:22 -07:00
proto.h mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
ptrace.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
rtc.c rtc: rework rtc_register_device() resource management 2020-11-19 12:50:12 +01:00
setup.c alpha: switch from DISCONTIGMEM to SPARSEMEM 2020-12-15 12:13:42 -08:00
signal.c alpha: add support for TIF_NOTIFY_SIGNAL 2020-12-12 09:16:34 -07:00
smc37c93x.c arch: mostly remove <asm/segment.h> 2019-04-23 21:51:40 +02:00
smc37c669.c arch: mostly remove <asm/segment.h> 2019-04-23 21:51:40 +02:00
smp.c sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
srm_env.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
srmcons.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
sys_alcor.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_cabriolet.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_dp264.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_eb64p.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_eiger.c alpha: remove unneeded semicolon in sys_eiger.c 2020-06-12 17:43:17 -07:00
sys_jensen.c genirq: Move irq_has_action() into core code 2020-12-15 16:19:30 +01:00
sys_marvel.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_miata.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_mikasa.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_nautilus.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_noritake.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_rawhide.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_ruffian.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_rx164.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_sable.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_sio.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_sx164.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_takara.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_titan.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
sys_wildfire.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
systbls.S alpha: syscalls: switch to generic syscalltbl.sh 2021-04-25 05:25:22 +09:00
time.c alpha: Replace setup_irq() by request_irq() 2020-03-29 21:03:41 +02:00
traps.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
vmlinux.lds.S vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG 2020-09-01 09:50:35 +02:00