linux-kernel - Re: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for better performance

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Message-ID: <CAEf4BzYiSfyZky+Axab6BwN55cyoY9N-0p7DA9R2OFr=ZdjS5Q@mail.gmail.com>
Date: Fri, 30 Aug 2024 10:55:04 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: kernel test robot <lkp@...el.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, linux-trace-kernel@...r.kernel.org, 
	peterz@...radead.org, oleg@...hat.com, llvm@...ts.linux.dev, 
	oe-kbuild-all@...ts.linux.dev, rostedt@...dmis.org, mhiramat@...nel.org, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, jolsa@...nel.org, 
	paulmck@...nel.org, willy@...radead.org, surenb@...gle.com, 
	akpm@...ux-foundation.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for
 better performance

On Fri, Aug 30, 2024 at 10:42 AM kernel test robot <lkp@...el.com> wrote:
>
> Hi Andrii,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on tip/perf/core]
> [also build test ERROR on next-20240830]
> [cannot apply to perf-tools-next/perf-tools-next perf-tools/perf-tools linus/master acme/perf/core v6.11-rc5]
> [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/Andrii-Nakryiko/uprobes-revamp-uprobe-refcounting-and-lifetime-management/20240830-024135
> base:   tip/perf/core
> patch link:    https://lore.kernel.org/r/20240829183741.3331213-9-andrii%40kernel.org
> patch subject: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for better performance
> config: i386-buildonly-randconfig-004-20240830 (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-lkp@intel.com/config)
> compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-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/202408310130.t9EBKteQ-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> kernel/events/uprobes.c:1157:2: error: call to undeclared function 'synchronize_rcu_tasks_trace'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     1157 |         synchronize_rcu_tasks_trace();
>          |         ^
>    kernel/events/uprobes.c:1157:2: note: did you mean 'synchronize_rcu_tasks_rude'?
>    include/linux/rcupdate.h:206:6: note: 'synchronize_rcu_tasks_rude' declared here
>      206 | void synchronize_rcu_tasks_rude(void);
>          |      ^
>    1 error generated.

Missing #include <linux/rcupdate_trace.h>, will add.

>
>
> vim +/synchronize_rcu_tasks_trace +1157 kernel/events/uprobes.c
>
>   1145
>   1146  void uprobe_unregister_sync(void)
>   1147  {
>   1148          /*
>   1149           * Now that handler_chain() and handle_uretprobe_chain() iterate over
>   1150           * uprobe->consumers list under RCU protection without holding
>   1151           * uprobe->register_rwsem, we need to wait for RCU grace period to
>   1152           * make sure that we can't call into just unregistered
>   1153           * uprobe_consumer's callbacks anymore. If we don't do that, fast and
>   1154           * unlucky enough caller can free consumer's memory and cause
>   1155           * handler_chain() or handle_uretprobe_chain() to do an use-after-free.
>   1156           */
> > 1157          synchronize_rcu_tasks_trace();
>   1158  }
>   1159  EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
>   1160
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki