Warning: This file is not a C or C++ file. It does not have highlighting.
| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
|---|---|
| 2 | /* |
| 3 | * Detect Hung Task: detecting tasks stuck in D state |
| 4 | * |
| 5 | * Copyright (C) 2025 Tongcheng Travel (www.ly.com) |
| 6 | * Author: Lance Yang <mingzhe.yang@ly.com> |
| 7 | */ |
| 8 | #ifndef __LINUX_HUNG_TASK_H |
| 9 | #define __LINUX_HUNG_TASK_H |
| 10 | |
| 11 | #include <linux/bug.h> |
| 12 | #include <linux/sched.h> |
| 13 | #include <linux/compiler.h> |
| 14 | |
| 15 | /* |
| 16 | * @blocker: Combines lock address and blocking type. |
| 17 | * |
| 18 | * Since lock pointers are at least 4-byte aligned(32-bit) or 8-byte |
| 19 | * aligned(64-bit). This leaves the 2 least bits (LSBs) of the pointer |
| 20 | * always zero. So we can use these bits to encode the specific blocking |
| 21 | * type. |
| 22 | * |
| 23 | * Note that on architectures where this is not guaranteed, or for any |
| 24 | * unaligned lock, this tracking mechanism is silently skipped for that |
| 25 | * lock. |
| 26 | * |
| 27 | * Type encoding: |
| 28 | * 00 - Blocked on mutex (BLOCKER_TYPE_MUTEX) |
| 29 | * 01 - Blocked on semaphore (BLOCKER_TYPE_SEM) |
| 30 | * 10 - Blocked on rw-semaphore as READER (BLOCKER_TYPE_RWSEM_READER) |
| 31 | * 11 - Blocked on rw-semaphore as WRITER (BLOCKER_TYPE_RWSEM_WRITER) |
| 32 | */ |
| 33 | #define BLOCKER_TYPE_MUTEX 0x00UL |
| 34 | #define BLOCKER_TYPE_SEM 0x01UL |
| 35 | #define BLOCKER_TYPE_RWSEM_READER 0x02UL |
| 36 | #define BLOCKER_TYPE_RWSEM_WRITER 0x03UL |
| 37 | |
| 38 | #define BLOCKER_TYPE_MASK 0x03UL |
| 39 | |
| 40 | #ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER |
| 41 | static inline void hung_task_set_blocker(void *lock, unsigned long type) |
| 42 | { |
| 43 | unsigned long lock_ptr = (unsigned long)lock; |
| 44 | |
| 45 | WARN_ON_ONCE(!lock_ptr); |
| 46 | WARN_ON_ONCE(READ_ONCE(current->blocker)); |
| 47 | |
| 48 | /* |
| 49 | * If the lock pointer matches the BLOCKER_TYPE_MASK, return |
| 50 | * without writing anything. |
| 51 | */ |
| 52 | if (lock_ptr & BLOCKER_TYPE_MASK) |
| 53 | return; |
| 54 | |
| 55 | WRITE_ONCE(current->blocker, lock_ptr | type); |
| 56 | } |
| 57 | |
| 58 | static inline void hung_task_clear_blocker(void) |
| 59 | { |
| 60 | WRITE_ONCE(current->blocker, 0UL); |
| 61 | } |
| 62 | |
| 63 | /* |
| 64 | * hung_task_get_blocker_type - Extracts blocker type from encoded blocker |
| 65 | * address. |
| 66 | * |
| 67 | * @blocker: Blocker pointer with encoded type (via LSB bits) |
| 68 | * |
| 69 | * Returns: BLOCKER_TYPE_MUTEX, BLOCKER_TYPE_SEM, etc. |
| 70 | */ |
| 71 | static inline unsigned long hung_task_get_blocker_type(unsigned long blocker) |
| 72 | { |
| 73 | WARN_ON_ONCE(!blocker); |
| 74 | |
| 75 | return blocker & BLOCKER_TYPE_MASK; |
| 76 | } |
| 77 | |
| 78 | static inline void *hung_task_blocker_to_lock(unsigned long blocker) |
| 79 | { |
| 80 | WARN_ON_ONCE(!blocker); |
| 81 | |
| 82 | return (void *)(blocker & ~BLOCKER_TYPE_MASK); |
| 83 | } |
| 84 | #else |
| 85 | static inline void hung_task_set_blocker(void *lock, unsigned long type) |
| 86 | { |
| 87 | } |
| 88 | static inline void hung_task_clear_blocker(void) |
| 89 | { |
| 90 | } |
| 91 | static inline unsigned long hung_task_get_blocker_type(unsigned long blocker) |
| 92 | { |
| 93 | return 0UL; |
| 94 | } |
| 95 | static inline void *hung_task_blocker_to_lock(unsigned long blocker) |
| 96 | { |
| 97 | return NULL; |
| 98 | } |
| 99 | #endif |
| 100 | |
| 101 | #endif /* __LINUX_HUNG_TASK_H */ |
| 102 |
Warning: This file is not a C or C++ file. It does not have highlighting.