kernel/context_tracking.c:80: warning: Function parameter or member 'state' not described in '__ct_user_enter'

From: kernel test robot
Date: Sun Oct 22 2023 - 22:44:35 EST

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tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 05d3ef8bba77c1b5f98d941d8b2d4aeab8118ef1
commit: e67198cc05b8ecbb7b8e2d8ef9fb5c8d26821873 context_tracking: Take idle eqs entrypoints over RCU
date: 1 year, 4 months ago
config: x86_64-alldefconfig (https://download.01.org/0day-ci/archive/20231023/202310231046.sRQwwdnk-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231023/202310231046.sRQwwdnk-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310231046.sRQwwdnk-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> kernel/context_tracking.c:80: warning: Function parameter or member 'state' not described in '__ct_user_enter'
>> kernel/context_tracking.c:184: warning: Function parameter or member 'state' not described in '__ct_user_exit'

vim +80 kernel/context_tracking.c

aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 69
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 70 /**
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 71 * __ct_user_enter - Inform the context tracking that the CPU is going
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 72 * to enter user or guest space mode.
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 73 *
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 74 * This function must be called right before we switch from the kernel
3aab4f50bff89bd Rik van Riel 2015-02-10 75 * to user or guest space, when it's guaranteed the remaining kernel
3aab4f50bff89bd Rik van Riel 2015-02-10 76 * instructions to execute won't use any RCU read side critical section
3aab4f50bff89bd Rik van Riel 2015-02-10 77 * because this function sets RCU in extended quiescent state.
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 78 */
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 79 void noinstr __ct_user_enter(enum ctx_state state)
91d1aa43d30505b Frederic Weisbecker 2012-11-27 @80 {
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 81 /* Kernel threads aren't supposed to go to userspace */
91d1aa43d30505b Frederic Weisbecker 2012-11-27 82 WARN_ON_ONCE(!current->mm);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 83
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 84 if (!context_tracking_recursion_enter())
d0e536d89395ecd Paolo Bonzini 2015-10-28 85 return;
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 86
3aab4f50bff89bd Rik van Riel 2015-02-10 87 if ( __this_cpu_read(context_tracking.state) != state) {
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 88 if (__this_cpu_read(context_tracking.active)) {
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 89 /*
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 90 * At this stage, only low level arch entry code remains and
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 91 * then we'll run in userspace. We can assume there won't be
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 92 * any RCU read-side critical section until the next call to
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 93 * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 94 * on the tick.
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 95 */
19fdd98b6253404 Rik van Riel 2015-02-10 96 if (state == CONTEXT_USER) {
0372007f5a79d61 Thomas Gleixner 2020-03-04 97 instrumentation_begin();
19fdd98b6253404 Rik van Riel 2015-02-10 98 trace_user_enter(0);
abf917cd91cbb73 Frederic Weisbecker 2012-07-25 99 vtime_user_enter(current);
0372007f5a79d61 Thomas Gleixner 2020-03-04 100 instrumentation_end();
19fdd98b6253404 Rik van Riel 2015-02-10 101 }
91d1aa43d30505b Frederic Weisbecker 2012-11-27 102 rcu_user_enter();
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 103 }
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 104 /*
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 105 * Even if context tracking is disabled on this CPU, because it's outside
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 106 * the full dynticks mask for example, we still have to keep track of the
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 107 * context transitions and states to prevent inconsistency on those of
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 108 * other CPUs.
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 109 * If a task triggers an exception in userspace, sleep on the exception
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 110 * handler and then migrate to another CPU, that new CPU must know where
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 111 * the exception returns by the time we call exception_exit().
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 112 * This information can only be provided by the previous CPU when it called
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 113 * exception_enter().
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 114 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 115 * is false because we know that CPU is not tickless.
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 116 */
3aab4f50bff89bd Rik van Riel 2015-02-10 117 __this_cpu_write(context_tracking.state, state);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 118 }
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 119 context_tracking_recursion_exit();
d0e536d89395ecd Paolo Bonzini 2015-10-28 120 }
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 121 EXPORT_SYMBOL_GPL(__ct_user_enter);
d0e536d89395ecd Paolo Bonzini 2015-10-28 122
f67671baadf6dba Frederic Weisbecker 2022-06-08 123 /*
f67671baadf6dba Frederic Weisbecker 2022-06-08 124 * OBSOLETE:
f67671baadf6dba Frederic Weisbecker 2022-06-08 125 * This function should be noinstr but the below local_irq_restore() is
f67671baadf6dba Frederic Weisbecker 2022-06-08 126 * unsafe because it involves illegal RCU uses through tracing and lockdep.
f67671baadf6dba Frederic Weisbecker 2022-06-08 127 * This is unlikely to be fixed as this function is obsolete. The preferred
f67671baadf6dba Frederic Weisbecker 2022-06-08 128 * way is to call __context_tracking_enter() through user_enter_irqoff()
f67671baadf6dba Frederic Weisbecker 2022-06-08 129 * or context_tracking_guest_enter(). It should be the arch entry code
f67671baadf6dba Frederic Weisbecker 2022-06-08 130 * responsibility to call into context tracking with IRQs disabled.
f67671baadf6dba Frederic Weisbecker 2022-06-08 131 */
fe98db1c6d1ad73 Frederic Weisbecker 2022-06-08 132 void ct_user_enter(enum ctx_state state)
d0e536d89395ecd Paolo Bonzini 2015-10-28 133 {
d0e536d89395ecd Paolo Bonzini 2015-10-28 134 unsigned long flags;
d0e536d89395ecd Paolo Bonzini 2015-10-28 135
d0e536d89395ecd Paolo Bonzini 2015-10-28 136 /*
d0e536d89395ecd Paolo Bonzini 2015-10-28 137 * Some contexts may involve an exception occuring in an irq,
d0e536d89395ecd Paolo Bonzini 2015-10-28 138 * leading to that nesting:
d0e536d89395ecd Paolo Bonzini 2015-10-28 139 * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
d0e536d89395ecd Paolo Bonzini 2015-10-28 140 * This would mess up the dyntick_nesting count though. And rcu_irq_*()
d0e536d89395ecd Paolo Bonzini 2015-10-28 141 * helpers are enough to protect RCU uses inside the exception. So
d0e536d89395ecd Paolo Bonzini 2015-10-28 142 * just return immediately if we detect we are in an IRQ.
d0e536d89395ecd Paolo Bonzini 2015-10-28 143 */
d0e536d89395ecd Paolo Bonzini 2015-10-28 144 if (in_interrupt())
d0e536d89395ecd Paolo Bonzini 2015-10-28 145 return;
d0e536d89395ecd Paolo Bonzini 2015-10-28 146
d0e536d89395ecd Paolo Bonzini 2015-10-28 147 local_irq_save(flags);
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 148 __ct_user_enter(state);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 149 local_irq_restore(flags);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 150 }
fe98db1c6d1ad73 Frederic Weisbecker 2022-06-08 151 NOKPROBE_SYMBOL(ct_user_enter);
fe98db1c6d1ad73 Frederic Weisbecker 2022-06-08 152 EXPORT_SYMBOL_GPL(ct_user_enter);
3aab4f50bff89bd Rik van Riel 2015-02-10 153
f163f0302ab6972 Frederic Weisbecker 2022-06-08 154 /**
f163f0302ab6972 Frederic Weisbecker 2022-06-08 155 * user_enter_callable() - Unfortunate ASM callable version of user_enter() for
f163f0302ab6972 Frederic Weisbecker 2022-06-08 156 * archs that didn't manage to check the context tracking
f163f0302ab6972 Frederic Weisbecker 2022-06-08 157 * static key from low level code.
f163f0302ab6972 Frederic Weisbecker 2022-06-08 158 *
f163f0302ab6972 Frederic Weisbecker 2022-06-08 159 * This OBSOLETE function should be noinstr but it unsafely calls
f163f0302ab6972 Frederic Weisbecker 2022-06-08 160 * local_irq_restore(), involving illegal RCU uses through tracing and lockdep.
f67671baadf6dba Frederic Weisbecker 2022-06-08 161 * This is unlikely to be fixed as this function is obsolete. The preferred
f67671baadf6dba Frederic Weisbecker 2022-06-08 162 * way is to call user_enter_irqoff(). It should be the arch entry code
f67671baadf6dba Frederic Weisbecker 2022-06-08 163 * responsibility to call into context tracking with IRQs disabled.
f67671baadf6dba Frederic Weisbecker 2022-06-08 164 */
f163f0302ab6972 Frederic Weisbecker 2022-06-08 165 void user_enter_callable(void)
3aab4f50bff89bd Rik van Riel 2015-02-10 166 {
f70cd6b07e629f3 Paolo Bonzini 2015-10-28 167 user_enter();
3aab4f50bff89bd Rik van Riel 2015-02-10 168 }
f163f0302ab6972 Frederic Weisbecker 2022-06-08 169 NOKPROBE_SYMBOL(user_enter_callable);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 170
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 171 /**
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 172 * __ct_user_exit - Inform the context tracking that the CPU is
3aab4f50bff89bd Rik van Riel 2015-02-10 173 * exiting user or guest mode and entering the kernel.
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 174 *
3aab4f50bff89bd Rik van Riel 2015-02-10 175 * This function must be called after we entered the kernel from user or
3aab4f50bff89bd Rik van Riel 2015-02-10 176 * guest space before any use of RCU read side critical section. This
3aab4f50bff89bd Rik van Riel 2015-02-10 177 * potentially include any high level kernel code like syscalls, exceptions,
3aab4f50bff89bd Rik van Riel 2015-02-10 178 * signal handling, etc...
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 179 *
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 180 * This call supports re-entrancy. This way it can be called from any exception
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 181 * handler without needing to know if we came from userspace or not.
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 182 */
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 183 void noinstr __ct_user_exit(enum ctx_state state)
91d1aa43d30505b Frederic Weisbecker 2012-11-27 @184 {
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 185 if (!context_tracking_recursion_enter())
d0e536d89395ecd Paolo Bonzini 2015-10-28 186 return;
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 187
3aab4f50bff89bd Rik van Riel 2015-02-10 188 if (__this_cpu_read(context_tracking.state) == state) {
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 189 if (__this_cpu_read(context_tracking.active)) {
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 190 /*
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 191 * We are going to run code that may use RCU. Inform
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 192 * RCU core about that (ie: we may need the tick again).
4eacdf18374e5d7 Frederic Weisbecker 2013-01-16 193 */
91d1aa43d30505b Frederic Weisbecker 2012-11-27 194 rcu_user_exit();
19fdd98b6253404 Rik van Riel 2015-02-10 195 if (state == CONTEXT_USER) {
0372007f5a79d61 Thomas Gleixner 2020-03-04 196 instrumentation_begin();
abf917cd91cbb73 Frederic Weisbecker 2012-07-25 197 vtime_user_exit(current);
1b6a259aa5ab16d Frederic Weisbecker 2013-07-11 198 trace_user_exit(0);
0372007f5a79d61 Thomas Gleixner 2020-03-04 199 instrumentation_end();
d65ec12127a5b6c Frederic Weisbecker 2013-07-11 200 }
19fdd98b6253404 Rik van Riel 2015-02-10 201 }
c467ea763fd5d87 Frederic Weisbecker 2015-03-04 202 __this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
91d1aa43d30505b Frederic Weisbecker 2012-11-27 203 }
aed5ed47724f6a7 Frederic Weisbecker 2015-05-06 204 context_tracking_recursion_exit();
d0e536d89395ecd Paolo Bonzini 2015-10-28 205 }
0ffc781a19ed303 Frederic Weisbecker 2022-06-08 206 EXPORT_SYMBOL_GPL(__ct_user_exit);
d0e536d89395ecd Paolo Bonzini 2015-10-28 207

:::::: The code at line 80 was first introduced by commit
:::::: 91d1aa43d30505b0b825db8898ffc80a8eca96c7 context_tracking: New context tracking susbsystem

:::::: TO: Frederic Weisbecker <fweisbec@xxxxxxxxx>
:::::: CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>

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