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Wander Lairson Costa 3b1107abdc 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 11:11:00 +02:00
arch MIPS: Only fiddle with CHECKFLAGS if `need-compiler' 2023-09-19 12:28:10 +02:00
block blk-throttle: consider 'carryover_ios/bytes' in throtl_trim_slice() 2023-09-19 12:28:00 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto X.509: if signature is unsupported skip validation 2023-09-13 09:43:03 +02:00
Documentation dt-bindings: clock: xlnx,versal-clk: drop select:false 2023-09-19 12:27:57 +02:00
drivers ACPICA: Add AML_NO_OPERAND_RESOLVE flag to Timer 2023-09-23 11:11:00 +02:00
fs locks: fix KASAN: use-after-free in trace_event_raw_event_filelock_lock 2023-09-23 11:11:00 +02:00
include kernel/fork: beware of __put_task_struct() calling context 2023-09-23 11:11:00 +02:00
init sched/psi: Select KERNFS as needed 2023-09-13 09:42:28 +02:00
io_uring io_uring: Don't set affinity on a dying sqpoll thread 2023-09-19 12:27:54 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel kernel/fork: beware of __put_task_struct() calling context 2023-09-23 11:11:00 +02:00
lib kunit: Fix wild-memory-access bug in kunit_free_suite_set() 2023-09-19 12:28:08 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm Multi-gen LRU: avoid race in inc_min_seq() 2023-09-19 12:28:04 +02:00
net kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg(). 2023-09-19 12:28:10 +02:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:08:18 +02:00
samples samples/bpf: fix broken map lookup probe 2023-09-13 09:42:34 +02:00
scripts kconfig: fix possible buffer overflow 2023-09-19 12:27:59 +02:00
security smackfs: Prevent underflow in smk_set_cipso() 2023-09-13 09:42:42 +02:00
sound ASoC: tegra: Fix SFC conversion for few rates 2023-09-19 12:27:56 +02:00
tools selftests: Keep symlinks, when possible 2023-09-19 12:28:08 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add() 2023-09-13 09:42:46 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS devlink: move code to a dedicated directory 2023-08-30 16:11:00 +02:00
Makefile Linux 6.1.54 2023-09-19 12:28:10 +02:00
README

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.