No description
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Andrea Righi c01adf4097 sched_ext: Add RCU protection to scx_root in DSQ iterator
Using a DSQ iterators from a timer callback can trigger the following
lockdep splat when accessing scx_root:

 =============================
 WARNING: suspicious RCU usage
 6.14.0-virtme #1 Not tainted
 -----------------------------
 kernel/sched/ext.c:6907 suspicious rcu_dereference_check() usage!

 other info that might help us debug this:

 rcu_scheduler_active = 2, debug_locks = 1
 no locks held by swapper/0/0.

 stack backtrace:
 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.14.0-virtme #1 PREEMPT(full)
 Sched_ext: tickless (enabled+all)
 Call Trace:
 <IRQ>
 dump_stack_lvl+0x6f/0xb0
 lockdep_rcu_suspicious.cold+0x4e/0xa3
 bpf_iter_scx_dsq_new+0xb1/0xd0
 bpf_prog_63f4fd1bccc101e7_dispatch_cpu+0x3e/0x156
 bpf_prog_8320d4217989178c_dispatch_all_cpus+0x153/0x1b6
 bpf_prog_97f847d871513f95_sched_timerfn+0x4c/0x264
 ? hrtimer_run_softirq+0x4f/0xd0
 bpf_timer_cb+0x7a/0x140
 __hrtimer_run_queues+0x1f9/0x3a0
 hrtimer_run_softirq+0x8c/0xd0
 handle_softirqs+0xd3/0x3d0
 __irq_exit_rcu+0x9a/0xc0
 irq_exit_rcu+0xe/0x20
 sysvec_apic_timer_interrupt+0x73/0x80

Add a proper dereference check to explicitly validate RCU-safe access to
scx_root from rcu_read_lock() contexts and also from contexts that hold
rcu_read_lock_bh(), such as timer callbacks.

Fixes: cdf5a6faa8 ("sched_ext: Move dsq_hash into scx_sched")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
History 2025-04-30 12:39:50 -10:00
arch
block
certs
crypto
Documentation
drivers
fs
include
init
io_uring
ipc
kernel
lib
LICENSES
mm
net
rust
samples
scripts
security
sound
tools
usr
virt
.clang-format
.clippy.toml
.cocciconfig
.editorconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile
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 reStructuredText 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.