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Date: Tue, 29 Nov 2022 04:30:45 +0800
From: kernel test robot <lkp@...el.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Will Deacon <will@...nel.org>, Jan Kara <jack@...e.cz>
Cc: oe-kbuild-all@...ts.linux.dev, Waiman Long <longman@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <rostedt@...dmis.org>,
Mel Gorman <mgorman@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Catalin Marinas <catalin.marinas@....com>
Subject: Re: Re: Crash with PREEMPT_RT on aarch64 machine
Hi Sebastian,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on tip/locking/core]
[also build test WARNING on linus/master v6.1-rc7 next-20221128]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Sebastian-Andrzej-Siewior/Re-Crash-with-PREEMPT_RT-on-aarch64-machine/20221129-000000
patch link: https://lore.kernel.org/r/Y4Tapja2qq8HiHBZ%40linutronix.de
patch subject: Re: Crash with PREEMPT_RT on aarch64 machine
config: m68k-allyesconfig
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/d4aea399f0b5472dc15a4c623d99b4ae79005050
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Sebastian-Andrzej-Siewior/Re-Crash-with-PREEMPT_RT-on-aarch64-machine/20221129-000000
git checkout d4aea399f0b5472dc15a4c623d99b4ae79005050
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash kernel/
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
In file included from include/asm-generic/bug.h:7,
from arch/m68k/include/asm/bug.h:32,
from include/linux/bug.h:5,
from include/linux/thread_info.h:13,
from include/asm-generic/preempt.h:5,
from ./arch/m68k/include/generated/asm/preempt.h:1,
from include/linux/preempt.h:78,
from include/linux/spinlock.h:56,
from kernel/locking/rtmutex_api.c:5:
kernel/locking/rtmutex.c: In function 'rt_mutex_set_owner':
>> kernel/locking/rtmutex.c:100:79: warning: comparison between pointer and integer
100 | WARN_ON_ONCE(cmpxchg_acquire(&lock->owner, RT_MUTEX_HAS_WAITERS, val) != RT_MUTEX_HAS_WAITERS);
| ^~
include/linux/once_lite.h:28:41: note: in definition of macro 'DO_ONCE_LITE_IF'
28 | bool __ret_do_once = !!(condition); \
| ^~~~~~~~~
kernel/locking/rtmutex.c:100:9: note: in expansion of macro 'WARN_ON_ONCE'
100 | WARN_ON_ONCE(cmpxchg_acquire(&lock->owner, RT_MUTEX_HAS_WAITERS, val) != RT_MUTEX_HAS_WAITERS);
| ^~~~~~~~~~~~
In file included from ./arch/m68k/include/generated/asm/rwonce.h:1,
from include/linux/compiler.h:246,
from include/linux/build_bug.h:5,
from include/linux/container_of.h:5,
from include/linux/list.h:5,
from include/linux/preempt.h:11:
kernel/locking/rtmutex.c: In function 'rt_mutex_set_owner_pi':
>> include/asm-generic/rwonce.h:55:37: warning: assignment to 'struct task_struct *' from 'long unsigned int' makes pointer from integer without a cast [-Wint-conversion]
55 | *(volatile typeof(x) *)&(x) = (val); \
| ^
include/asm-generic/rwonce.h:61:9: note: in expansion of macro '__WRITE_ONCE'
61 | __WRITE_ONCE(x, val); \
| ^~~~~~~~~~~~
kernel/locking/rtmutex.c:117:9: note: in expansion of macro 'WRITE_ONCE'
117 | WRITE_ONCE(lock->owner, val);
| ^~~~~~~~~~
vim +100 kernel/locking/rtmutex.c
64
65 /*
66 * lock->owner state tracking:
67 *
68 * lock->owner holds the task_struct pointer of the owner. Bit 0
69 * is used to keep track of the "lock has waiters" state.
70 *
71 * owner bit0
72 * NULL 0 lock is free (fast acquire possible)
73 * NULL 1 lock is free and has waiters and the top waiter
74 * is going to take the lock*
75 * taskpointer 0 lock is held (fast release possible)
76 * taskpointer 1 lock is held and has waiters**
77 *
78 * The fast atomic compare exchange based acquire and release is only
79 * possible when bit 0 of lock->owner is 0.
80 *
81 * (*) It also can be a transitional state when grabbing the lock
82 * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock,
83 * we need to set the bit0 before looking at the lock, and the owner may be
84 * NULL in this small time, hence this can be a transitional state.
85 *
86 * (**) There is a small time when bit 0 is set but there are no
87 * waiters. This can happen when grabbing the lock in the slow path.
88 * To prevent a cmpxchg of the owner releasing the lock, we need to
89 * set this bit before looking at the lock.
90 */
91
92 static __always_inline void
93 rt_mutex_set_owner(struct rt_mutex_base *lock, struct task_struct *owner)
94 {
95 unsigned long val = (unsigned long)owner;
96
97 if (rt_mutex_has_waiters(lock))
98 val |= RT_MUTEX_HAS_WAITERS;
99
> 100 WARN_ON_ONCE(cmpxchg_acquire(&lock->owner, RT_MUTEX_HAS_WAITERS, val) != RT_MUTEX_HAS_WAITERS);
101 }
102
--
0-DAY CI Kernel Test Service
https://01.org/lkp
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