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