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f1a0a376ca
linux/arch/ia64/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
acpi-ext.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
acpi.c ia64: ensure proper NUMA distance and possible map initialization 2021-04-30 11:20:34 -07:00
asm-offsets.c ia64: do not typedef struct pal_min_state_area_s 2021-02-12 05:11:19 +09:00
audit.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
brl_emu.c signal: Remove the task parameter from force_sig_fault 2019-05-29 09:31:43 -05:00
crash_dump.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crash.c Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
cyclone.c remove ioremap_nocache and devm_ioremap_nocache 2020-01-06 09:45:59 +01:00
dma-mapping.c dma-mapping: split <linux/dma-mapping.h> 2020-10-06 07:07:03 +02:00
efi_stub.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
efi.c ia64: fix EFI_DEBUG build 2021-04-30 11:20:35 -07:00
elfcore.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
entry.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
entry.S ia64: syscalls: switch to generic syscalltbl.sh 2021-04-25 05:25:40 +09:00
err_inject.c ia64: fix format strings for err_inject 2021-03-25 09:22:55 -07:00
esi_stub.S treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
esi.c efi/ia64: Use existing helpers to locate ESI table 2020-02-23 21:59:42 +01:00
fsys.S arch/ia64/kernel/fsys.S: fix typos 2021-04-30 11:20:34 -07:00
fsyscall_gtod_data.h Stop ia64 being the last holdout using GENERIC_TIME_VSYSCALL_OLD 2017-11-13 12:15:40 -08:00
ftrace.c maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault 2020-06-17 10:57:41 -07:00
gate-data.S
gate.lds.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
gate.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head.S ia64: drop unused IA64_FW_EMU ifdef 2021-04-30 11:20:35 -07:00
iosapic.c locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header 2020-08-06 16:13:13 +02:00
irq_ia64.c ia64: Remove perfmon 2020-09-11 09:34:32 -07:00
irq_lsapic.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 locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header 2020-08-06 16:13:13 +02:00
irq.h ia64: replace setup_irq() by request_irq() 2020-03-13 15:21:28 -07:00
ivt.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
kprobes.c ia64: kprobes: Use generic kretprobe trampoline handler 2020-09-08 11:52:33 +02:00
machine_kexec.c ia64: drop marked broken DISCONTIGMEM and VIRTUAL_MEM_MAP 2021-04-30 11:20:35 -07:00
Makefile ia64: drop marked broken DISCONTIGMEM and VIRTUAL_MEM_MAP 2021-04-30 11:20:35 -07:00
Makefile.gate ia64: require -Wl,--hash-style=sysv 2019-05-18 11:29:01 +09:00
mca_asm.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
mca_drv_asm.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mca_drv.c ia64: do not typedef struct pal_min_state_area_s 2021-02-12 05:11:19 +09:00
mca_drv.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mca.c ia64: mca: always make IA64_MCA_DEBUG an expression 2021-04-30 11:20:35 -07:00
minstate.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
module.c ia64: module: fix symbolizer crash on fdescr 2021-04-30 11:20:35 -07:00
msi_ia64.c ia64: remove now unused machvec indirections 2019-08-16 11:33:57 -07:00
numa.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
pal.S ia64: trivial spelling fixes 2021-04-30 11:20:35 -07:00
palinfo.c arch: ia64: Remove rest of perfmon support 2021-01-22 12:12:20 +05:30
patch.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pci-dma.c ia64 for v5.4 - big change here is removal of support for SGI Altix 2019-09-16 15:32:01 -07:00
perfmon_itanium.h arch: ia64: Remove rest of perfmon support 2021-01-22 12:12:20 +05:30
process.c arch: setup PF_IO_WORKER threads like PF_KTHREAD 2021-02-21 17:25:22 -07:00
ptrace.c ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls 2021-03-13 11:27:31 -08:00
relocate_kernel.S mm: reorder includes after introduction of linux/pgtable.h 2020-06-09 09:39:13 -07:00
sal.c locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header 2020-08-06 16:13:13 +02:00
salinfo.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
setup.c locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header 2020-08-06 16:13:13 +02:00
sigframe.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
signal.c ia64: don't call handle_signal() unless there's actually a signal queued 2021-03-02 17:22:11 -07:00
smp.c A set of locking fixes and updates: 2020-08-10 19:07:44 -07:00
smpboot.c sched/core: Initialize the idle task with preemption disabled 2021-05-12 13:01:45 +02:00
stacktrace.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sys_ia64.c ia64: remove CONFIG_PCI ifdefs 2019-08-16 11:33:57 -07:00
time.c EFI updates for v5.12 2021-02-20 19:09:26 -08:00
topology.c ia64: remove CONFIG_ACPI ifdefs 2019-08-16 11:33:57 -07:00
traps.c signal: Remove the task parameter from force_sig_fault 2019-05-29 09:31:43 -05:00
unaligned.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
uncached.c efi: ia64: move IA64-only declarations to new asm/efi.h header 2021-01-18 13:50:37 +01:00
unwind_decoder.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
unwind_i.h ia64: kernel: unwind_i.h: Replace zero-length array with flexible-array 2020-06-15 23:08:31 -05:00
unwind.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