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- Revert "tracing: Remove pid in task_rename tracing output" A change was made to remove the pid field from the task_rename event because it was thought that it was always done for the current task and recording the pid would be redundant. This turned out to be incorrect and there are a few corner case where this is not true and caused some regressions in tooling. - Fix the reading from user space for migration The reading of user space uses a seq lock type of logic where it uses a per-cpu temporary buffer and disables migration, then enables preemption, does the copy from user space, disables preemption, enables migration and checks if there was any schedule switches while preemption was enabled. If there was a context switch, then it is considered that the per-cpu buffer could be corrupted and it tries again. There's a protection check that tests if it takes a hundred tries, it issues a warning and exits out to prevent a live lock. This was triggered because the task was selected by the load balancer to be migrated to another CPU, every time preemption is enabled the migration task would schedule in try to migrate the task but can't because migration is disabled and let it run again. This caused the scheduler to schedule out the task every time it enabled preemption and made the loop never exit (until the 100 iteration test triggered). Fix this by enabling and disabling preemption and keeping migration enabled if the reading from user space needs to be done again. This will let the migration thread migrate the task and the copy from user space will likely pass on the next iteration. - Fix trace_marker copy option freeing The "copy_trace_marker" option allows a tracing instance to get a copy of a write to the trace_marker file of the top level instance. This is managed by a link list protected by RCU. When an instance is removed, a check is made if the option is set, and if so synchronized_rcu() is called. The problem is that an iteration is made to reset all the flags to what they were when the instance was created (to perform clean ups) was done before the check of the copy_trace_marker option and that option was cleared, so the synchronize_rcu() was never called. Move the clearing of all the flags after the check of copy_trace_marker to do synchronize_rcu() so that the option is still set if it was before and the synchronization is performed. - Fix entries setting when validating the persistent ring buffer When validating the persistent ring buffer on boot up, the number of events per sub-buffer is added to the sub-buffer meta page. The validator was updating cpu_buffer->head_page (the first sub-buffer of the per-cpu buffer) and not the "head_page" variable that was iterating the sub-buffers. This was causing the first sub-buffer to be assigned the entries for each sub-buffer and not the sub-buffer that was supposed to be updated. - Use "hash" value to update the direct callers When updating the ftrace direct callers, it assigned a temporary callback to all the callback functions of the ftrace ops and not just the functions represented by the passed in hash. This causes an unnecessary slow down of the functions of the ftrace_ops that is not being modified. Only update the functions that are going to be modified to call the ftrace loop function so that the update can be made on those functions. -----BEGIN PGP SIGNATURE----- iIoEABYKADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCacAMahQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qr0sAQCoI4L3iAR5HU1z8dw2GWhOz9fTnzfw 9VPRZAsga9J5xgEA1Y0bvKBM0UPHFAL2POkaILYV1aT00lZ7aIVHPqfdYgA= =OoGW -----END PGP SIGNATURE----- Merge tag 'trace-v7.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Revert "tracing: Remove pid in task_rename tracing output" A change was made to remove the pid field from the task_rename event because it was thought that it was always done for the current task and recording the pid would be redundant. This turned out to be incorrect and there are a few corner case where this is not true and caused some regressions in tooling. - Fix the reading from user space for migration The reading of user space uses a seq lock type of logic where it uses a per-cpu temporary buffer and disables migration, then enables preemption, does the copy from user space, disables preemption, enables migration and checks if there was any schedule switches while preemption was enabled. If there was a context switch, then it is considered that the per-cpu buffer could be corrupted and it tries again. There's a protection check that tests if it takes a hundred tries, it issues a warning and exits out to prevent a live lock. This was triggered because the task was selected by the load balancer to be migrated to another CPU, every time preemption is enabled the migration task would schedule in try to migrate the task but can't because migration is disabled and let it run again. This caused the scheduler to schedule out the task every time it enabled preemption and made the loop never exit (until the 100 iteration test triggered). Fix this by enabling and disabling preemption and keeping migration enabled if the reading from user space needs to be done again. This will let the migration thread migrate the task and the copy from user space will likely pass on the next iteration. - Fix trace_marker copy option freeing The "copy_trace_marker" option allows a tracing instance to get a copy of a write to the trace_marker file of the top level instance. This is managed by a link list protected by RCU. When an instance is removed, a check is made if the option is set, and if so synchronized_rcu() is called. The problem is that an iteration is made to reset all the flags to what they were when the instance was created (to perform clean ups) was done before the check of the copy_trace_marker option and that option was cleared, so the synchronize_rcu() was never called. Move the clearing of all the flags after the check of copy_trace_marker to do synchronize_rcu() so that the option is still set if it was before and the synchronization is performed. - Fix entries setting when validating the persistent ring buffer When validating the persistent ring buffer on boot up, the number of events per sub-buffer is added to the sub-buffer meta page. The validator was updating cpu_buffer->head_page (the first sub-buffer of the per-cpu buffer) and not the "head_page" variable that was iterating the sub-buffers. This was causing the first sub-buffer to be assigned the entries for each sub-buffer and not the sub-buffer that was supposed to be updated. - Use "hash" value to update the direct callers When updating the ftrace direct callers, it assigned a temporary callback to all the callback functions of the ftrace ops and not just the functions represented by the passed in hash. This causes an unnecessary slow down of the functions of the ftrace_ops that is not being modified. Only update the functions that are going to be modified to call the ftrace loop function so that the update can be made on those functions. * tag 'trace-v7.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ftrace: Use hash argument for tmp_ops in update_ftrace_direct_mod ring-buffer: Fix to update per-subbuf entries of persistent ring buffer tracing: Fix trace_marker copy link list updates tracing: Fix failure to read user space from system call trace events tracing: Revert "tracing: Remove pid in task_rename tracing output" |
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| README | ||
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