Changes in hung_task.c

0fc8f6200d2313278fbf4539bbab74677c685531 - Merge drm/drm-fixes into drm-misc-fixes

Mon, 27 Apr 2026 08:26:49 +0000

Merge drm/drm-fixes into drm-misc-fixesGetting fixes and updates from v7.1-rc1.Signed-off-by: Thomas Zimmermann List of files: /linux/kernel/hung_task.c

f4b369c6fe0ceaba2da2daff8c9eb415f85926dd - Merge branch 'next' into for-linus

Mon, 20 Apr 2026 01:28:57 +0000

Merge branch 'next' into for-linusPrepare input updates for 7.1 merge window. List of files: /linux/kernel/hung_task.c

440d6635b20037bc9ad46b20817d7b61cef0fc1b - Merge tag 'mm-nonmm-stable-2026-04-15-04-20' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Fri, 17 Apr 2026 03:11:56 +0000

Merge tag 'mm-nonmm-stable-2026-04-15-04-20' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mmPull non-MM updates from Andrew Morton: - "pid: make sub-init creation retryable" (Oleg Nesterov) Make creation of init in a new namespace more robust by clearing away some historical cruft which is no longer needed. Also some documentation fixups - "selftests/fchmodat2: Error handling and general" (Mark Brown) Fix and a cleanup for the fchmodat2() syscall selftest - "lib: polynomial: Move to math/ and clean up" (Andy Shevchenko) - "hung_task: Provide runtime reset interface for hung task detector" (Aaron Tomlin) Give administrators the ability to zero out /proc/sys/kernel/hung_task_detect_count - "tools/getdelays: use the static UAPI headers from tools/include/uapi" (Thomas Weißschuh) Teach getdelays to use the in-kernel UAPI headers rather than the system-provided ones - "watchdog/hardlockup: Improvements to hardlockup" (Mayank Rungta) Several cleanups and fixups to the hardlockup detector code and its documentation - "lib/bch: fix undefined behavior from signed left-shifts" (Josh Law) A couple of small/theoretical fixes in the bch code - "ocfs2/dlm: fix two bugs in dlm_match_regions()" (Junrui Luo) - "cleanup the RAID5 XOR library" (Christoph Hellwig) A quite far-reaching cleanup to this code. I can't do better than to quote Christoph: "The XOR library used for the RAID5 parity is a bit of a mess right now. The main file sits in crypto/ despite not being cryptography and not using the crypto API, with the generic implementations sitting in include/asm-generic and the arch implementations sitting in an asm/ header in theory. The latter doesn't work for many cases, so architectures often build the code directly into the core kernel, or create another module for the architecture code. Change this to a single module in lib/ that also contains the architecture optimizations, similar to the library work Eric Biggers has done for the CRC and crypto libraries later. After that it changes to better calling conventions that allow for smarter architecture implementations (although none is contained here yet), and uses static_call to avoid indirection function call overhead" - "lib/list_sort: Clean up list_sort() scheduling workarounds" (Kuan-Wei Chiu) Clean up this library code by removing a hacky thing which was added for UBIFS, which UBIFS doesn't actually need - "Fix bugs in extract_iter_to_sg()" (Christian Ehrhardt) Fix a few bugs in the scatterlist code, add in-kernel tests for the now-fixed bugs and fix a leak in the test itself - "kdump: Enable LUKS-encrypted dump target support in ARM64 and PowerPC" (Coiby Xu) Enable support of the LUKS-encrypted device dump target on arm64 and powerpc - "ocfs2: consolidate extent list validation into block read callbacks" (Joseph Qi) Cleanup, simplify, and make more robust ocfs2's validation of extent list fields (Kernel test robot loves mounting corrupted fs images!)* tag 'mm-nonmm-stable-2026-04-15-04-20' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (127 commits) ocfs2: validate group add input before caching ocfs2: validate bg_bits during freefrag scan ocfs2: fix listxattr handling when the buffer is full doc: watchdog: fix typos etc update Sean's email address ocfs2: use get_random_u32() where appropriate ocfs2: split transactions in dio completion to avoid credit exhaustion ocfs2: remove redundant l_next_free_rec check in __ocfs2_find_path() ocfs2: validate extent block list fields during block read ocfs2: remove empty extent list check in ocfs2_dx_dir_lookup_rec() ocfs2: validate dx_root extent list fields during block read ocfs2: fix use-after-free in ocfs2_fault() when VM_FAULT_RETRY ocfs2: handle invalid dinode in ocfs2_group_extend .get_maintainer.ignore: add Askar ocfs2: validate bg_list extent bounds in discontig groups checkpatch: exclude forward declarations of const structs tools/accounting: handle truncated taskstats netlink messages taskstats: set version in TGID exit notifications ocfs2/heartbeat: fix slot mapping rollback leaks on error paths arm64,ppc64le/kdump: pass dm-crypt keys to kdump kernel ... List of files: /linux/kernel/hung_task.c

73d40c42f6aa1702f685261911429bf5265f78d5 - hung_task: explicitly report I/O wait state in log output

Tue, 03 Mar 2026 22:13:24 +0000

hung_task: explicitly report I/O wait state in log outputCurrently, the hung task reporting mechanism indiscriminately labels allTASK_UNINTERRUPTIBLE (D) tasks as "blocked", irrespective of whether theyare awaiting I/O completion or kernel locking primitives. This ambiguitycompels system administrators to manually inspect stack traces to discernwhether the delay stems from an I/O wait (typically indicative of hardwareor filesystem anomalies) or software contention. Such detailed analysisis not always immediately accessible to system administrators or supportengineers.To address this, this patch utilises the existing in_iowait field withinstruct task_struct to augment the failure report. If the task is blockeddue to I/O (e.g., via io_schedule_prepare()), the log message is updatedto explicitly state "blocked in I/O wait".Examples: - Standard Block: "INFO: task bash:123 blocked for more than 120 seconds". - I/O Block: "INFO: task dd:456 blocked in I/O wait for more than 120 seconds".Theoretically, concurrent executions of io_schedule_finish() could resultin a race condition where the read flag does not precisely correlate withthe subsequently printed backtrace. However, this limitation is deemedacceptable in practice. The entire reporting mechanism is inherently racyby design; nevertheless, it remains highly reliable in the vast majorityof cases, particularly because it primarily captures protracted stalls. Consequently, introducing additional synchronisation to mitigate thisminor inaccuracy would be entirely disproportionate to the situation.Link: https://lkml.kernel.org/r/20260303221324.4106917-1-atomlin@atomlin.comSigned-off-by: Aaron Tomlin Acked-by: Masami Hiramatsu (Google) Reviewed-by: Petr Mladek Cc: Greg Kroah-Hartman Cc: Lance Yang Signed-off-by: Andrew Morton List of files: /linux/kernel/hung_task.c

5eaef7f8ee40150cbd78a7b445001929bb2d2031 - hung_task: increment the global counter immediately

Tue, 03 Mar 2026 20:30:31 +0000

hung_task: increment the global counter immediatelyA recent change allowed to reset the global counter of hung tasks usingthe sysctl interface. A potential race with the regular check has beensolved by updating the global counter only once at the end of the check.However, the hung task check can take a significant amount of time,particularly when task information is being dumped to slow serialconsoles. Some users monitor this global counter to trigger immediatemigration of critical containers. Delaying the increment until the fullcheck completes postpones these high-priority rescue operations.Update the global counter as soon as a hung task is detected. Since thevalue is read asynchronously, a relaxed atomic operation is sufficient.Link: https://lkml.kernel.org/r/20260303203031.4097316-4-atomlin@atomlin.comSigned-off-by: Petr Mladek Signed-off-by: Aaron Tomlin Reported-by: Lance Yang Closes: https://lore.kernel.org/r/f239e00f-4282-408d-b172-0f9885f4b01b@linux.devReviewed-by: Aaron Tomlin Reviewed-by: Lance Yang Cc: Greg Kroah-Hartman Cc: Joel Granados Cc: Masami Hiramatsu (Google) Signed-off-by: Andrew Morton List of files: /linux/kernel/hung_task.c

49085e1b70f898695b63594ff559f5a243589b83 - hung_task: enable runtime reset of hung_task_detect_count

Tue, 03 Mar 2026 20:30:30 +0000

hung_task: enable runtime reset of hung_task_detect_countCurrently, the hung_task_detect_count sysctl provides a cumulative countof hung tasks since boot. In long-running, high-availabilityenvironments, this counter may lose its utility if it cannot be reset oncean incident has been resolved. Furthermore, the previous implementationrelied upon implicit ordering, which could not strictly guarantee thatdiagnostic metadata published by one CPU was visible to the panic logic onanother.This patch introduces the capability to reset the detection count bywriting "0" to the hung_task_detect_count sysctl. The proc_handler logichas been updated to validate this input and atomically reset the counter.The synchronisation of sysctl_hung_task_detect_count relies upon atransactional model to ensure the integrity of the detection counteragainst concurrent resets from userspace. The application ofatomic_long_read_acquire() and atomic_long_cmpxchg_release() is correctand provides the following guarantees: 1. Prevention of Load-Store Reordering via Acquire Semantics By utilising atomic_long_read_acquire() to snapshot the counter before initiating the task traversal, we establish a strict memory barrier. This prevents the compiler or hardware from reordering the initial load to a point later in the scan. Without this "acquire" barrier, a delayed load could potentially read a "0" value resulting from a userspace reset that occurred mid-scan. This would lead to the subsequent cmpxchg succeeding erroneously, thereby overwriting the user's reset with stale increment data. 2. Atomicity of the "Commit" Phase via Release Semantics The atomic_long_cmpxchg_release() serves as the transaction's commit point. The "release" barrier ensures that all diagnostic recordings and task-state observations made during the scan are globally visible before the counter is incremented. 3. Race Condition Resolution This pairing effectively detects any "out-of-band" reset of the counter. If sysctl_hung_task_detect_count is modified via the procfs interface during the scan, the final cmpxchg will detect the discrepancy between the current value and the "acquire" snapshot. Consequently, the update will fail, ensuring that a reset command from the administrator is prioritised over a scan that may have been invalidated by that very reset.Link: https://lkml.kernel.org/r/20260303203031.4097316-3-atomlin@atomlin.comSigned-off-by: Aaron Tomlin Reviewed-by: Masami Hiramatsu (Google) Reviewed-by: Joel Granados Reviewed-by: Petr Mladek Cc: Greg Kroah-Hartman Cc: Lance Yang Signed-off-by: Andrew Morton List of files: /linux/kernel/hung_task.c

00b5cdeb9fe761654d5a76a411c79b8ff04a81e5 - hung_task: refactor detection logic and atomicise detection count

Tue, 03 Mar 2026 20:30:29 +0000

hung_task: refactor detection logic and atomicise detection countPatch series "hung_task: Provide runtime reset interface for hung taskdetector", v9.This series introduces the ability to reset/proc/sys/kernel/hung_task_detect_count.Writing a "0" value to this file atomically resets the counter of detectedhung tasks. This functionality provides system administrators with themeans to clear the cumulative diagnostic history following incidentresolution, thereby simplifying subsequent monitoring withoutnecessitating a system restart.This patch (of 3):The check_hung_task() function currently conflates two distinctresponsibilities: validating whether a task is hung and handling thesubsequent reporting (printing warnings, triggering panics, ortracepoints).This patch refactors the logic by introducing hung_task_info(), a functiondedicated solely to reporting. The actual detection check,task_is_hung(), is hoisted into the primary loop withincheck_hung_uninterruptible_tasks(). This separation clearly decouples themechanism of detection from the policy of reporting.Furthermore, to facilitate future support for concurrent hung taskdetection, the global sysctl_hung_task_detect_count variable is convertedfrom unsigned long to atomic_long_t. Consequently, the counting logic isupdated to accumulate the number of hung tasks locally (this_round_count)during the iteration. The global counter is then updated atomically viaatomic_long_cmpxchg_relaxed() once the loop concludes, rather thanincrementally during the scan.These changes are strictly preparatory and introduce no functional changeto the system's runtime behaviour.Link: https://lkml.kernel.org/r/20260303203031.4097316-1-atomlin@atomlin.comLink: https://lkml.kernel.org/r/20260303203031.4097316-2-atomlin@atomlin.comSigned-off-by: Aaron Tomlin Reviewed-by: Masami Hiramatsu (Google) Reviewed-by: Petr Mladek Cc: Greg Kroah-Hartman Cc: Lance Yang Cc: Masami Hiramatsu Cc: Joel Granados Signed-off-by: Andrew Morton List of files: /linux/kernel/hung_task.c

0421ccdfad0d92713a812a5aeb7d07b0ea7213c8 - Merge tag 'v7.0-rc3' into next

Thu, 12 Mar 2026 17:44:42 +0000

Merge tag 'v7.0-rc3' into nextSync up with the mainline to brig up the latest changes, specificallychanges to ALPS driver. List of files: /linux/kernel/hung_task.c

ec496f77b4c11036cc835d6f045fb5e5ef1e6530 - Merge branch 'for-6.20/sony' into for-linus

Mon, 09 Feb 2026 16:33:26 +0000

Merge branch 'for-6.20/sony' into for-linus- Support for Rock band 4 PS4 and PS5 guitars (Rosalie Wanders) List of files: /linux/kernel/hung_task.c

cc4adab164b772a34b3340d644b7c4728498581e - Merge tag 'v6.19-rc1' into msm-next

Tue, 20 Jan 2026 22:06:55 +0000

Merge tag 'v6.19-rc1' into msm-nextMerge Linux 6.19-rc1 in order to catch up with other changes (e.g. UBWCconfig database defining UBWC_6).Signed-off-by: Dmitry Baryshkov List of files: /linux/kernel/hung_task.c

24f171c7e145f43b9f187578e89b0982ce87e54c - Merge tag 'asoc-fix-v6.19-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

Sun, 21 Dec 2025 10:11:11 +0000

Merge tag 'asoc-fix-v6.19-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linusASoC: Fixes for v6.19We've been quite busy with fixes since the merge window, though not inany particularly exciting ways - the standout thing is the fix for _SXcontrols which were broken by a change to how we do clamping, otherwiseit's all fairly run of the mill fixes and quirks. List of files: /linux/kernel/hung_task.c

5add3c3c280a35f7e258e9cef7607db5a2e56fdc - Merge drm/drm-next into drm-xe-next

Fri, 19 Dec 2025 10:51:22 +0000

Merge drm/drm-next into drm-xe-nextBackmerging to bring in 6.19-rc1. An important upstream bugfix andto help unblock PTL CI.Signed-off-by: Thomas Hellström List of files: /linux/kernel/hung_task.c

ec439c38013550420aecc15988ae6acb670838c1 - Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf after 6.19-rc1

Wed, 17 Dec 2025 05:29:38 +0000

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf after 6.19-rc1Cross-merge BPF and other fixes after downstream PR.Signed-off-by: Alexei Starovoitov List of files: /linux/kernel/hung_task.c

b8304863a3990d0f18c38e5b94191830a63ee1af - Merge drm/drm-next into drm-intel-next

Mon, 15 Dec 2025 13:24:02 +0000

Merge drm/drm-next into drm-intel-nextSync-up some display code needed for Async flips refactor.Signed-off-by: Rodrigo Vivi List of files: /linux/kernel/hung_task.c

84318277d6334c6981ab326d4acc87c6a6ddc9b8 - Merge remote-tracking branch 'drm/drm-fixes' into drm-misc-fixes

Mon, 15 Dec 2025 11:53:27 +0000

Merge remote-tracking branch 'drm/drm-fixes' into drm-misc-fixesPull in rc1 to include all changes since the merge window closed,and grab all fixes and changes from drm/drm-next.Signed-off-by: Maarten Lankhorst List of files: /linux/kernel/hung_task.c

7f790dd21a931c61167f7bdc327aecf2cebad327 - Merge drm/drm-next into drm-misc-next

Mon, 15 Dec 2025 08:27:39 +0000

Merge drm/drm-next into drm-misc-nextLet's kickstart the v6.20 (7.0?) release cycle.Signed-off-by: Maxime Ripard List of files: /linux/kernel/hung_task.c

a4a508df2aa34f8650afde54ea804321c618f45f - Merge tag 'v6.18' into next

Sat, 13 Dec 2025 09:18:20 +0000

Merge tag 'v6.18' into nextSync up with the mainline to bring in the latest APIs. List of files: /linux/kernel/hung_task.c

509d3f45847627f4c5cdce004c3ec79262b5239c - Merge tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Sat, 06 Dec 2025 22:01:20 +0000

Merge tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mmPull non-MM updates from Andrew Morton: - "panic: sys_info: Refactor and fix a potential issue" (Andy Shevchenko) fixes a build issue and does some cleanup in ib/sys_info.c - "Implement mul_u64_u64_div_u64_roundup()" (David Laight) enhances the 64-bit math code on behalf of a PWM driver and beefs up the test module for these library functions - "scripts/gdb/symbols: make BPF debug info available to GDB" (Ilya Leoshkevich) makes BPF symbol names, sizes, and line numbers available to the GDB debugger - "Enable hung_task and lockup cases to dump system info on demand" (Feng Tang) adds a sysctl which can be used to cause additional info dumping when the hung-task and lockup detectors fire - "lib/base64: add generic encoder/decoder, migrate users" (Kuan-Wei Chiu) adds a general base64 encoder/decoder to lib/ and migrates several users away from their private implementations - "rbree: inline rb_first() and rb_last()" (Eric Dumazet) makes TCP a little faster - "liveupdate: Rework KHO for in-kernel users" (Pasha Tatashin) reworks the KEXEC Handover interfaces in preparation for Live Update Orchestrator (LUO), and possibly for other future clients - "kho: simplify state machine and enable dynamic updates" (Pasha Tatashin) increases the flexibility of KEXEC Handover. Also preparation for LUO - "Live Update Orchestrator" (Pasha Tatashin) is a major new feature targeted at cloud environments. Quoting the cover letter: This series introduces the Live Update Orchestrator, a kernel subsystem designed to facilitate live kernel updates using a kexec-based reboot. This capability is critical for cloud environments, allowing hypervisors to be updated with minimal downtime for running virtual machines. LUO achieves this by preserving the state of selected resources, such as memory, devices and their dependencies, across the kernel transition. As a key feature, this series includes support for preserving memfd file descriptors, which allows critical in-memory data, such as guest RAM or any other large memory region, to be maintained in RAM across the kexec reboot. Mike Rappaport merits a mention here, for his extensive review and testing work. - "kexec: reorganize kexec and kdump sysfs" (Sourabh Jain) moves the kexec and kdump sysfs entries from /sys/kernel/ to /sys/kernel/kexec/ and adds back-compatibility symlinks which can hopefully be removed one day - "kho: fixes for vmalloc restoration" (Mike Rapoport) fixes a BUG which was being hit during KHO restoration of vmalloc() regions* tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (139 commits) calibrate: update header inclusion Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()" vmcoreinfo: track and log recoverable hardware errors kho: fix restoring of contiguous ranges of order-0 pages kho: kho_restore_vmalloc: fix initialization of pages array MAINTAINERS: TPM DEVICE DRIVER: update the W-tag init: replace simple_strtoul with kstrtoul to improve lpj_setup KHO: fix boot failure due to kmemleak access to non-PRESENT pages Documentation/ABI: new kexec and kdump sysfs interface Documentation/ABI: mark old kexec sysfs deprecated kexec: move sysfs entries to /sys/kernel/kexec test_kho: always print restore status kho: free chunks using free_page() instead of kfree() selftests/liveupdate: add kexec test for multiple and empty sessions selftests/liveupdate: add simple kexec-based selftest for LUO selftests/liveupdate: add userspace API selftests docs: add documentation for memfd preservation via LUO mm: memfd_luo: allow preserving memfd liveupdate: luo_file: add private argument to store runtime state mm: shmem: export some functions to internal.h ... List of files: /linux/kernel/hung_task.c

2ace52718376fdb56aca863da2eebe70d7e2ddb1 - Merge branch 'objtool/core'

Fri, 21 Nov 2025 10:21:20 +0000

Merge branch 'objtool/core'Bring in the UDB and objtool data annotations to avoid conflicts while further extending the bug exceptions.Signed-off-by: Peter Zijlstra List of files: /linux/kernel/hung_task.c

8b2b9b4f6f4f7a61b7e323479ed7d9faa21d6287 - hung_task: add hung_task_sys_info sysctl to dump sys info on task-hung

Thu, 13 Nov 2025 11:10:37 +0000

hung_task: add hung_task_sys_info sysctl to dump sys info on task-hungWhen task-hung happens, developers may need different kinds of systeminformation (call-stacks, memory info, locks, etc.) to help debugging.Add 'hung_task_sys_info' sysctl knob to take human readable string like"tasks,mem,timers,locks,ftrace,...", and when task-hung happens, allrequested information will be dumped. (refer kernel/sys_info.c for moredetails).Meanwhile, the newly introduced sys_info() call is used to unify someexisting info-dumping knobs.[feng.tang@linux.alibaba.com: maintain consistecy established behavior, per Lance and Petr] Link: https://lkml.kernel.org/r/aRncJo1mA5Zk77Hr@U-2FWC9VHC-2323.localLink: https://lkml.kernel.org/r/20251113111039.22701-3-feng.tang@linux.alibaba.comSigned-off-by: Feng Tang Suggested-by: Petr Mladek Reviewed-by: Petr Mladek Reviewed-by: Lance Yang Cc: Jonathan Corbet Cc: "Paul E . McKenney" Cc: Steven Rostedt Signed-off-by: Andrew Morton List of files: /linux/kernel/hung_task.c