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Message-ID: <202408270455.R85TrPfw-lkp@intel.com>
Date: Tue, 27 Aug 2024 04:32:49 +0800
From: kernel test robot <lkp@...el.com>
To: Ahmed Ehab <bottaawesome633@...il.com>, linux-kernel@...r.kernel.org
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Valentin Schneider <vschneid@...hat.com>,
linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] Refactor switch_mm_cid() to avoid unnecessary checks
Hi Ahmed,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/sched/core]
[also build test ERROR on linus/master v6.11-rc5 next-20240826]
[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/Ahmed-Ehab/Refactor-switch_mm_cid-to-avoid-unnecessary-checks/20240826-153216
base: tip/sched/core
patch link: https://lore.kernel.org/r/20240824223132.11925-1-bottaawesome633%40gmail.com
patch subject: [PATCH] Refactor switch_mm_cid() to avoid unnecessary checks
config: arm-ep93xx_defconfig (https://download.01.org/0day-ci/archive/20240827/202408270455.R85TrPfw-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240827/202408270455.R85TrPfw-lkp@intel.com/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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202408270455.R85TrPfw-lkp@intel.com/
All errors (new ones prefixed by >>):
>> kernel/sched/core.c:5232:4: error: implicit declaration of function 'switch_mm_cid_from_user_to_kernel' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
switch_mm_cid_from_user_to_kernel(rq, prev, next);
^
>> kernel/sched/core.c:5257:4: error: implicit declaration of function 'switch_mm_cid_from_kernel_to_user' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
switch_mm_cid_from_kernel_to_user(rq, prev, next);
^
>> kernel/sched/core.c:5259:4: error: implicit declaration of function 'switch_mm_cid_from_user_to_user' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
switch_mm_cid_from_user_to_user(rq, prev, next);
^
3 errors generated.
vim +/switch_mm_cid_from_user_to_kernel +5232 kernel/sched/core.c
5199
5200 /*
5201 * context_switch - switch to the new MM and the new thread's register state.
5202 */
5203 static __always_inline struct rq *
5204 context_switch(struct rq *rq, struct task_struct *prev,
5205 struct task_struct *next, struct rq_flags *rf)
5206 {
5207 prepare_task_switch(rq, prev, next);
5208
5209 /*
5210 * For paravirt, this is coupled with an exit in switch_to to
5211 * combine the page table reload and the switch backend into
5212 * one hypercall.
5213 */
5214 arch_start_context_switch(prev);
5215
5216 /*
5217 * kernel -> kernel lazy + transfer active
5218 * user -> kernel lazy + mmgrab_lazy_tlb() active
5219 *
5220 * kernel -> user switch + mmdrop_lazy_tlb() active
5221 * user -> user switch
5222 *
5223 * switch_mm_cid() needs to be updated if the barriers provided
5224 * by context_switch() are modified.
5225 */
5226 if (!next->mm) { // to kernel
5227 enter_lazy_tlb(prev->active_mm, next);
5228
5229 next->active_mm = prev->active_mm;
5230 if (prev->mm) { // from user
5231 mmgrab_lazy_tlb(prev->active_mm);
> 5232 switch_mm_cid_from_user_to_kernel(rq, prev, next);
5233 }
5234 else
5235 /*
5236 * kernel -> kernel transition does not change rq->curr->mm
5237 * state. It stays NULL.
5238 */
5239 prev->active_mm = NULL;
5240 } else { // to user
5241 membarrier_switch_mm(rq, prev->active_mm, next->mm);
5242 /*
5243 * sys_membarrier() requires an smp_mb() between setting
5244 * rq->curr / membarrier_switch_mm() and returning to userspace.
5245 *
5246 * The below provides this either through switch_mm(), or in
5247 * case 'prev->active_mm == next->mm' through
5248 * finish_task_switch()'s mmdrop().
5249 */
5250 switch_mm_irqs_off(prev->active_mm, next->mm, next);
5251 lru_gen_use_mm(next->mm);
5252
5253 if (!prev->mm) { // from kernel
5254 /* will mmdrop_lazy_tlb() in finish_task_switch(). */
5255 rq->prev_mm = prev->active_mm;
5256 prev->active_mm = NULL;
> 5257 switch_mm_cid_from_kernel_to_user(rq, prev, next);
5258 } else
> 5259 switch_mm_cid_from_user_to_user(rq, prev, next);
5260 }
5261
5262 prepare_lock_switch(rq, next, rf);
5263
5264 /* Here we just switch the register state and the stack. */
5265 switch_to(prev, next, prev);
5266 barrier();
5267
5268 return finish_task_switch(prev);
5269 }
5270
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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