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Namhyung Kim e1886b4731 perf/core: Fix slow perf_event_task_exit() with LBR callstacks 
[ Upstream commit 4960626f95 ]

I got a report that a task is stuck in perf_event_exit_task() waiting
for global_ctx_data_rwsem.  On large systems with lots threads, it'd
have performance issues when it grabs the lock to iterate all threads
in the system to allocate the context data.

And it'd block task exit path which is problematic especially under
memory pressure.

  perf_event_open
    perf_event_alloc
      attach_perf_ctx_data
        attach_global_ctx_data
          percpu_down_write (global_ctx_data_rwsem)
            for_each_process_thread
              alloc_task_ctx_data
                                               do_exit
                                                 perf_event_exit_task
                                                   percpu_down_read (global_ctx_data_rwsem)

It should not hold the global_ctx_data_rwsem on the exit path.  Let's
skip allocation for exiting tasks and free the data carefully.

Reported-by: Rosalie Fang <rosaliefang@google.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260112165157.1919624-1-namhyung@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:19:41 -05:00
arch perf/x86/intel: Add Airmont NP 2026-03-04 07:19:40 -05:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:19:38 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation ASoC: dt-bindings: asahi-kasei,ak5558: Fix the supply names 2026-02-26 14:59:46 -08:00
drivers irqchip/riscv-imsic: Add a CPU pm notifier to restore the IMSIC on exit 2026-03-04 07:19:39 -05:00
fs ntfs: ->d_compare() must not block 2026-03-04 07:19:34 -05:00
include EFI/CPER: don't go past the ARM processor CPER record buffer 2026-03-04 07:19:35 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/timeout: annotate data race in io_flush_timeouts() 2026-03-04 07:19:36 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel perf/core: Fix slow perf_event_task_exit() with LBR callstacks 2026-03-04 07:19:41 -05:00
lib objpool: fix the overestimation of object pooling metadata size 2026-02-26 14:59:36 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: fix false lockdep warning in __kfree_rcu_sheaf() 2026-02-26 14:59:14 -08:00
net bpf: net_sched: Use the correct destructor kfunc type 2026-03-04 07:19:40 -05:00
rust rust: cpufreq: always inline functions using build_assert with arguments 2026-03-04 07:19:37 -05:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts gendwarfksyms: Fix build on 32-bit hosts 2026-03-04 07:19:40 -05:00
security apparmor: fix aa_label to return state from compount and component match 2026-02-26 14:59:42 -08:00
sound ALSA: hda/realtek: Add quirk for Samsung Galaxy Book3 Pro 360 (NP965QFG) 2026-02-26 14:59:46 -08:00
tools tools/power cpupower: Reset errno before strtoull() 2026-03-04 07:19:33 -05:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.15 2026-02-27 16:05:10 -05:00
README README: Fix spelling 2024-03-18 03:36:32 -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 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.