/* SPDX-License-Identifier: GPL-2.0-only */ /* * Detect Hung Task: detecting tasks stuck in D state * * Copyright (C) 2025 Tongcheng Travel (www.ly.com) * Author: Lance Yang <mingzhe.yang@ly.com> */ #ifndef __LINUX_HUNG_TASK_H #define __LINUX_HUNG_TASK_H #include <linux/bug.h> #include <linux/sched.h> #include <linux/compiler.h> /* * @blocker: Combines lock address and blocking type. * * Since lock pointers are at least 4-byte aligned(32-bit) or 8-byte * aligned(64-bit). This leaves the 2 least bits (LSBs) of the pointer * always zero. So we can use these bits to encode the specific blocking * type. * * Type encoding: * 00 - Blocked on mutex (BLOCKER_TYPE_MUTEX) * 01 - Blocked on semaphore (BLOCKER_TYPE_SEM) * 10 - Blocked on rt-mutex (BLOCKER_TYPE_RTMUTEX) * 11 - Blocked on rw-semaphore (BLOCKER_TYPE_RWSEM) */ #define BLOCKER_TYPE_MUTEX 0x00UL #define BLOCKER_TYPE_SEM 0x01UL #define BLOCKER_TYPE_RTMUTEX 0x02UL #define BLOCKER_TYPE_RWSEM 0x03UL #define BLOCKER_TYPE_MASK 0x03UL #ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER static inline void hung_task_set_blocker(void *lock, unsigned long type) { unsigned long lock_ptr = (unsigned long)lock; WARN_ON_ONCE(!lock_ptr); WARN_ON_ONCE(READ_ONCE(current->blocker)); /* * If the lock pointer matches the BLOCKER_TYPE_MASK, return * without writing anything. */ if (WARN_ON_ONCE(lock_ptr & BLOCKER_TYPE_MASK)) return; WRITE_ONCE(current->blocker, lock_ptr | type); } static inline void hung_task_clear_blocker(void) { WARN_ON_ONCE(!READ_ONCE(current->blocker)); WRITE_ONCE(current->blocker, 0UL); } /* * hung_task_get_blocker_type - Extracts blocker type from encoded blocker * address. * * @blocker: Blocker pointer with encoded type (via LSB bits) * * Returns: BLOCKER_TYPE_MUTEX, BLOCKER_TYPE_SEM, etc. */ static inline unsigned long hung_task_get_blocker_type(unsigned long blocker) { WARN_ON_ONCE(!blocker); return blocker & BLOCKER_TYPE_MASK; } static inline void *hung_task_blocker_to_lock(unsigned long blocker) { WARN_ON_ONCE(!blocker); return (void *)(blocker & ~BLOCKER_TYPE_MASK); } #else static inline void hung_task_set_blocker(void *lock, unsigned long type) { } static inline void hung_task_clear_blocker(void) { } static inline unsigned long hung_task_get_blocker_type(unsigned long blocker) { return 0UL; } static inline void *hung_task_blocker_to_lock(unsigned long blocker) { return NULL; } #endif #endif /* __LINUX_HUNG_TASK_H */