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The deferred page initialization prevents debug objects from allocating slab pages until the initialization is complete. That causes depletion of the pool and disabling of debugobjects. The reason is that debugobjects uses __GFP_HIGH for allocations as it might be invoked from arbitrary contexts. When PREEMPT_COUNT is disabled there is no way to know whether the context is safe to set __GFP_KSWAPD_RECLAIM. This worked until v6.18. Since then allocations w/o a reclaim flag cause new_slab() to end up in alloc_frozen_pages_nolock_noprof(), which returns early when deferred page initialization has not yet completed. Work around that when PREEMPT_COUNT is enabled as the preempt counter allows debugobjects to add __GFP_KSWAPD_RECLAIM to the GFP flags when the context is preemtible. When PREEMPT_COUNT is disabled the context is unknown and the reclaim bit can't be set because the caller might hold locks which might deadlock in the allocator. That makes debugobjects depend on PREEMPT_COUNT || !DEFERRED_STRUCT_PAGE_INIT, which limits the coverage slightly, but keeps it functional for most cases. -----BEGIN PGP SIGNATURE----- iQJEBAABCgAuFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAmmka6wQHHRnbHhAa2Vy bmVsLm9yZwAKCRCmGPVMDXSYoaOrEACqslcovaH37JnDkEVuMJAl/RcHJbKfFL/s SN3UcPIDmae4yF+DVnMmLUjBdkuMHHkTQOQRGKuwpOT3PUqGxvYAYtd6JogH4joc LhMA6uJUddINScKvjJmvdUBwFWHRrrcO3QROdqjKrF/DUB1zGxGVsWDrvUT7xv7w sXa2IWNnC59Zo3LlRON4uO6S18wuKh2+Vo8cT579wRs4vrccNv0c6V9OnIyO8YCi yuYmaE+oTKgjZ5NOIwc/h5yV9g2TKod0s1eXdpfbSHdVvWL2qLH/CPUA3xyPgK04 X0Yy62MeaJ4gZZJEXnHJHnlgqZXOB34Xy6FvsrG9RL/iGOV30PNVpnZNxSzCjbvM qobG8R2x8ej+5/1tdybxmY9WLijTKF7rVeihNbyNJ3gcxAXtNx5kQsMeDDlHbyGV kqB2Z+w93GrzAfvUaE79QNehWQM7+3/pe0Z/tBPF78y0Fo50R0d8m35i87rqGFLq xipSNoFOPrvCkPOtb7Cui90Jh0LOvdMll1UT8TWXD5GjHUF02KuwEp80HruLIGTw zgSLLxgjR3EhPI6NtvNoQIpdt5tgIwcHIgUTUFkg1V74HK6Pa/LINREeP5so8VDh dEtHHU5Q9fl50/oPQn7f+tezvxKqrET/oZXnVgW2x21Ypf1IMdbQKawzNYu2YeWf aerqW8SBHw== =kvxN -----END PGP SIGNATURE----- Merge tag 'core-debugobjects-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull debugobjects fix from Thomas Gleixner: "A single fix for debugobjects. The deferred page initialization prevents debug objects from allocating slab pages until the initialization is complete. That causes depletion of the pool and disabling of debugobjects. The reason is that debugobjects uses __GFP_HIGH for allocations as it might be invoked from arbitrary contexts. When PREEMPT_COUNT is disabled there is no way to know whether the context is safe to set __GFP_KSWAPD_RECLAIM. This worked until v6.18. Since then allocations w/o a reclaim flag cause new_slab() to end up in alloc_frozen_pages_nolock_noprof(), which returns early when deferred page initialization has not yet completed. Work around that when PREEMPT_COUNT is enabled as the preempt counter allows debugobjects to add __GFP_KSWAPD_RECLAIM to the GFP flags when the context is preemtible. When PREEMPT_COUNT is disabled the context is unknown and the reclaim bit can't be set because the caller might hold locks which might deadlock in the allocator. That makes debugobjects depend on PREEMPT_COUNT || !DEFERRED_STRUCT_PAGE_INIT, which limits the coverage slightly, but keeps it functional for most cases" * tag 'core-debugobjects-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: debugobject: Make it work with deferred page initialization - again |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst