Re: [RFC PATCH v0.1 7/9] sched/umcg: add UMCG server/worker API (early RFC)

[kernel test robot <lkp@intel.com>]

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Hi Peter,

[FYI, it's a private test report for your RFC patch.]
[auto build test WARNING on tip/sched/core]
[also build test WARNING on tip/master]
[cannot apply to kselftest/next linus/master v5.13-rc2 next-20210521]
[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]

url:    https://github.com/0day-ci/linux/commits/Peter-Oskolkov/UMCG-early-preview-RFC-patchset/20210522-232442
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 1699949d3314e5d1956fb082e4cd4798bf6149fc
config: um-allmodconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/634e0c0b3bf5d6ede3674f9c754202b1a521ab89
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Peter-Oskolkov/UMCG-early-preview-RFC-patchset/20210522-232442
        git checkout 634e0c0b3bf5d6ede3674f9c754202b1a521ab89
        # save the attached .config to linux build tree
        make W=1 ARCH=um 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from kernel/sched/umcg.c:8:
   include/linux/syscalls.h:1062:57: error: unknown type name 'flags'
    1062 | asmlinkage long umcg_create_group(u32 api_version, u64, flags);
         |                                                         ^~~~~
   kernel/sched/umcg.c: In function '__do_sys_umcg_run_worker':
>> kernel/sched/umcg.c:889:27: warning: variable 'worker_ut' set but not used [-Wunused-but-set-variable]
     889 |  struct umcg_task __user *worker_ut;
         |                           ^~~~~~~~~
>> kernel/sched/umcg.c:888:27: warning: variable 'server_ut' set but not used [-Wunused-but-set-variable]
     888 |  struct umcg_task __user *server_ut;
         |                           ^~~~~~~~~


vim +/worker_ut +889 kernel/sched/umcg.c

   858	
   859	/**
   860	 * sys_umcg_run_worker - "run" a RUNNABLE worker as a server
   861	 * @flags:       reserved;
   862	 * @worker_tid:  tid of the worker to run;
   863	 * @ut:          the control struct umcg_task of the worker that blocked
   864	 *               during this "run".
   865	 *
   866	 * The worker must be in RUNNABLE state. The server (=current task)
   867	 * wakes the worker and blocks; when the worker, or one of the workers
   868	 * in umcg_swap chain, blocks, the server is woken and the syscall returns
   869	 * with ut indicating the blocked worker.
   870	 *
   871	 * If the worker exits or unregisters itself, the syscall succeeds with
   872	 * ut == NULL.
   873	 *
   874	 * Return:
   875	 * 0       - Ok;
   876	 * -EINTR  - a signal was received;
   877	 * -EINVAL - one of the parameters is wrong, or a precondition was not met.
   878	 */
   879	SYSCALL_DEFINE3(umcg_run_worker, u32, flags, u32, worker_tid,
   880			struct umcg_task __user **, ut)
   881	{
   882		int ret = -EINVAL;
   883		struct task_struct *worker;
   884		struct task_struct *server = current;
   885		struct umcg_task __user *result = NULL;
   886		struct umcg_task_data *worker_utd;
   887		struct umcg_task_data *server_utd;
 > 888		struct umcg_task __user *server_ut;
 > 889		struct umcg_task __user *worker_ut;
   890	
   891		if (!ut)
   892			return -EINVAL;
   893	
   894		rcu_read_lock();
   895		server_utd = rcu_dereference(server->umcg_task_data);
   896	
   897		if (!server_utd || server_utd->task_type != UMCG_TT_SERVER)
   898			goto out_rcu;
   899	
   900		if (flags)
   901			goto out_rcu;
   902	
   903		worker = find_get_task_by_vpid(worker_tid);
   904		if (!worker) {
   905			ret = -ESRCH;
   906			goto out_rcu;
   907		}
   908	
   909		worker_utd = rcu_dereference(worker->umcg_task_data);
   910		if (!worker_utd)
   911			goto out_rcu;
   912	
   913		if (!READ_ONCE(worker_utd->in_wait)) {
   914			ret = -EAGAIN;
   915			goto out_rcu;
   916		}
   917	
   918		if (server_utd->group != worker_utd->group)
   919			goto out_rcu;
   920	
   921		if (rcu_access_pointer(server_utd->peer) != worker)
   922			umcg_detach_peer();
   923	
   924		if (!rcu_access_pointer(server_utd->peer)) {
   925			umcg_lock_pair(server, worker);
   926			WARN_ON(worker_utd->peer);
   927			rcu_assign_pointer(server_utd->peer, worker);
   928			rcu_assign_pointer(worker_utd->peer, server);
   929			umcg_unlock_pair(server, worker);
   930		}
   931	
   932		server_ut = server_utd->umcg_task;
   933		worker_ut = server_utd->umcg_task;
   934	
   935		rcu_read_unlock();
   936	
   937		ret = do_context_switch(worker);
   938		if (ret)
   939			return ret;
   940	
   941		rcu_read_lock();
   942		worker = rcu_dereference(server_utd->peer);
   943		if (worker) {
   944			worker_utd = rcu_dereference(worker->umcg_task_data);
   945			if (worker_utd)
   946				result = worker_utd->umcg_task;
   947		}
   948		rcu_read_unlock();
   949	
   950		if (put_user(result, ut))
   951			return -EFAULT;
   952		return 0;
   953	
   954	out_rcu:
   955		rcu_read_unlock();
   956		return ret;
   957	}
   958	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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