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Wander Lairson Costa f1ceff37ac kernel/fork: beware of __put_task_struct() calling context [ Upstream commit `d243b34459` ] Under PREEMPT_RT, __put_task_struct() indirectly acquires sleeping locks. Therefore, it can't be called from an non-preemptible context. One practical example is splat inside inactive_task_timer(), which is called in a interrupt context: CPU: 1 PID: 2848 Comm: life Kdump: loaded Tainted: G W --------- Hardware name: HP ProLiant DL388p Gen8, BIOS P70 07/15/2012 Call Trace: dump_stack_lvl+0x57/0x7d mark_lock_irq.cold+0x33/0xba mark_lock+0x1e7/0x400 mark_usage+0x11d/0x140 __lock_acquire+0x30d/0x930 lock_acquire.part.0+0x9c/0x210 rt_spin_lock+0x27/0xe0 refill_obj_stock+0x3d/0x3a0 kmem_cache_free+0x357/0x560 inactive_task_timer+0x1ad/0x340 __run_hrtimer+0x8a/0x1a0 __hrtimer_run_queues+0x91/0x130 hrtimer_interrupt+0x10f/0x220 __sysvec_apic_timer_interrupt+0x7b/0xd0 sysvec_apic_timer_interrupt+0x4f/0xd0 asm_sysvec_apic_timer_interrupt+0x12/0x20 RIP: 0033:0x7fff196bf6f5 Instead of calling __put_task_struct() directly, we defer it using call_rcu(). A more natural approach would use a workqueue, but since in PREEMPT_RT, we can't allocate dynamic memory from atomic context, the code would become more complex because we would need to put the work_struct instance in the task_struct and initialize it when we allocate a new task_struct. The issue is reproducible with stress-ng: while true; do stress-ng --sched deadline --sched-period 1000000000 \ --sched-runtime 800000000 --sched-deadline \ 1000000000 --mmapfork 23 -t 20 done Reported-by: Hu Chunyu <chuhu@redhat.com> Suggested-by: Oleg Nesterov <oleg@redhat.com> Suggested-by: Valentin Schneider <vschneid@redhat.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Wander Lairson Costa <wander@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230614122323.37957-2-wander@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2023-09-23 11:09:55 +02:00
arch	MIPS: Only fiddle with CHECKFLAGS if `need-compiler'	2023-09-19 12:23:04 +02:00
block	block: don't add or resize partition on the disk with GENHD_FL_NO_PART	2023-09-19 12:23:03 +02:00
certs	certs/blacklist_hashes.c: fix const confusion in certs blacklist	2022-06-22 14:22:01 +02:00
crypto	X.509: if signature is unsupported skip validation	2023-09-19 12:22:52 +02:00
Documentation	dt-bindings: clock: xlnx,versal-clk: drop select:false	2023-09-19 12:22:56 +02:00
drivers	ACPICA: Add AML_NO_OPERAND_RESOLVE flag to Timer	2023-09-23 11:09:55 +02:00
fs	locks: fix KASAN: use-after-free in trace_event_raw_event_filelock_lock	2023-09-23 11:09:55 +02:00
include	kernel/fork: beware of __put_task_struct() calling context	2023-09-23 11:09:55 +02:00
init	x86/mm: Initialize text poking earlier	2023-08-08 19:58:33 +02:00
io_uring	io_uring: break iopolling on signal	2023-09-19 12:22:54 +02:00
ipc	ipc/sem: Fix dangling sem_array access in semtimedop race	2022-12-08 11:28:45 +01:00
kernel	kernel/fork: beware of __put_task_struct() calling context	2023-09-23 11:09:55 +02:00
lib	lib: test_scanf: Add explicit type cast to result initialization in test_number_prefix()	2023-09-19 12:23:01 +02:00
LICENSES	LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"	2021-07-15 06:31:24 -06:00
mm	mm/vmalloc: add a safer version of find_vm_area() for debug	2023-09-19 12:22:50 +02:00
net	kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg().	2023-09-19 12:23:04 +02:00
samples	samples/bpf: fix broken map lookup probe	2023-09-19 12:22:34 +02:00
scripts	kconfig: fix possible buffer overflow	2023-09-19 12:22:56 +02:00
security	smackfs: Prevent underflow in smk_set_cipso()	2023-09-19 12:22:39 +02:00
sound	ALSA: pcm: Fix missing fixup call in compat hw_refine ioctl	2023-09-19 12:22:50 +02:00
tools	kselftest/runner.sh: Propagate SIGTERM to runner child	2023-09-19 12:23:03 +02:00
usr	usr/include/Makefile: add linux/nfc.h to the compile-test coverage	2022-02-01 17:27:15 +01:00
virt	KVM: Grab a reference to KVM for VM and vCPU stats file descriptors	2023-08-03 10:22:40 +02:00
.clang-format	clang-format: Update with the latest for_each macro list	2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	.gitignore: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: add Andrej Shadura	2021-10-18 20:22:03 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Daniel Drake to credits	2021-09-21 08:34:58 +03:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	iio: stx104: Move to addac subdirectory	2023-08-26 14:23:27 +02:00
Makefile	Linux 5.15.132	2023-09-19 12:23:04 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.