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41 results

rcutree_trace.c

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    Paul E. McKenney authored and Paul E. McKenney committed
    Because newly offlined CPUs continue executing after completing the
    CPU_DYING notifiers, they legitimately enter the scheduler and use
    RCU while appearing to be offline.  This calls for a more sophisticated
    approach as follows:
    
    1.	RCU marks the CPU online during the CPU_UP_PREPARE phase.
    
    2.	RCU marks the CPU offline during the CPU_DEAD phase.
    
    3.	Diagnostics regarding use of read-side RCU by offline CPUs use
    	RCU's accounting rather than the cpu_online_map.  (Note that
    	__call_rcu() still uses cpu_online_map to detect illegal
    	invocations within CPU_DYING notifiers.)
    
    4.	Offline CPUs are prevented from hanging the system by
    	force_quiescent_state(), which pays attention to cpu_online_map.
    	Some additional work (in a later commit) will be needed to
    	guarantee that force_quiescent_state() waits a full jiffy before
    	assuming that a CPU is offline, for example, when called from
    	idle entry.  (This commit also makes the one-jiffy wait
    	explicit, since the old-style implicit wait can now be defeated
    	by RCU_FAST_NO_HZ and by rcutorture.)
    
    This approach avoids the false positives encountered when attempting to
    use more exact classification of CPU online/offline state.
    
    Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    2036d94a
    History
    rcutree_trace.c 13.75 KiB
    /*
     * Read-Copy Update tracing for classic implementation
     *
     * This program is free software; you can redistribute it and/or modify
     * it under the terms of the GNU General Public License as published by
     * the Free Software Foundation; either version 2 of the License, or
     * (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
     *
     * Copyright IBM Corporation, 2008
     *
     * Papers:  http://www.rdrop.com/users/paulmck/RCU
     *
     * For detailed explanation of Read-Copy Update mechanism see -
     *		Documentation/RCU
     *
     */
    #include <linux/types.h>
    #include <linux/kernel.h>
    #include <linux/init.h>
    #include <linux/spinlock.h>
    #include <linux/smp.h>
    #include <linux/rcupdate.h>
    #include <linux/interrupt.h>
    #include <linux/sched.h>
    #include <linux/atomic.h>
    #include <linux/bitops.h>
    #include <linux/module.h>
    #include <linux/completion.h>
    #include <linux/moduleparam.h>
    #include <linux/percpu.h>
    #include <linux/notifier.h>
    #include <linux/cpu.h>
    #include <linux/mutex.h>
    #include <linux/debugfs.h>
    #include <linux/seq_file.h>
    
    #define RCU_TREE_NONCORE
    #include "rcutree.h"
    
    #ifdef CONFIG_RCU_BOOST
    
    static char convert_kthread_status(unsigned int kthread_status)
    {
    	if (kthread_status > RCU_KTHREAD_MAX)
    		return '?';
    	return "SRWOY"[kthread_status];
    }
    
    #endif /* #ifdef CONFIG_RCU_BOOST */
    
    static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
    {
    	if (!rdp->beenonline)
    		return;
    	seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pgp=%lu qp=%d",
    		   rdp->cpu,
    		   cpu_is_offline(rdp->cpu) ? '!' : ' ',
    		   rdp->completed, rdp->gpnum,
    		   rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
    		   rdp->qs_pending);
    	seq_printf(m, " dt=%d/%llx/%d df=%lu",
    		   atomic_read(&rdp->dynticks->dynticks),
    		   rdp->dynticks->dynticks_nesting,
    		   rdp->dynticks->dynticks_nmi_nesting,
    		   rdp->dynticks_fqs);
    	seq_printf(m, " of=%lu", rdp->offline_fqs);
    	seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
    		   rdp->qlen_lazy, rdp->qlen,
    		   ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
    			rdp->nxttail[RCU_NEXT_TAIL]],
    		   ".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
    			rdp->nxttail[RCU_NEXT_READY_TAIL]],
    		   ".W"[rdp->nxttail[RCU_DONE_TAIL] !=
    			rdp->nxttail[RCU_WAIT_TAIL]],
    		   ".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]);
    #ifdef CONFIG_RCU_BOOST
    	seq_printf(m, " kt=%d/%c/%d ktl=%x",
    		   per_cpu(rcu_cpu_has_work, rdp->cpu),
    		   convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
    					  rdp->cpu)),
    		   per_cpu(rcu_cpu_kthread_cpu, rdp->cpu),
    		   per_cpu(rcu_cpu_kthread_loops, rdp->cpu) & 0xffff);
    #endif /* #ifdef CONFIG_RCU_BOOST */
    	seq_printf(m, " b=%ld", rdp->blimit);
    	seq_printf(m, " ci=%lu co=%lu ca=%lu\n",
    		   rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
    }
    
    #define PRINT_RCU_DATA(name, func, m) \
    	do { \
    		int _p_r_d_i; \
    		\
    		for_each_possible_cpu(_p_r_d_i) \
    			func(m, &per_cpu(name, _p_r_d_i)); \
    	} while (0)
    
    static int show_rcudata(struct seq_file *m, void *unused)
    {
    #ifdef CONFIG_TREE_PREEMPT_RCU
    	seq_puts(m, "rcu_preempt:\n");
    	PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data, m);
    #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
    	seq_puts(m, "rcu_sched:\n");
    	PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data, m);
    	seq_puts(m, "rcu_bh:\n");
    	PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data, m);
    	return 0;
    }
    
    static int rcudata_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcudata, NULL);
    }
    
    static const struct file_operations rcudata_fops = {
    	.owner = THIS_MODULE,
    	.open = rcudata_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
    {
    	if (!rdp->beenonline)
    		return;
    	seq_printf(m, "%d,%s,%lu,%lu,%d,%lu,%d",
    		   rdp->cpu,
    		   cpu_is_offline(rdp->cpu) ? "\"N\"" : "\"Y\"",
    		   rdp->completed, rdp->gpnum,
    		   rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
    		   rdp->qs_pending);
    	seq_printf(m, ",%d,%llx,%d,%lu",
    		   atomic_read(&rdp->dynticks->dynticks),
    		   rdp->dynticks->dynticks_nesting,
    		   rdp->dynticks->dynticks_nmi_nesting,
    		   rdp->dynticks_fqs);
    	seq_printf(m, ",%lu", rdp->offline_fqs);
    	seq_printf(m, ",%ld,%ld,\"%c%c%c%c\"", rdp->qlen_lazy, rdp->qlen,
    		   ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
    			rdp->nxttail[RCU_NEXT_TAIL]],
    		   ".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
    			rdp->nxttail[RCU_NEXT_READY_TAIL]],
    		   ".W"[rdp->nxttail[RCU_DONE_TAIL] !=
    			rdp->nxttail[RCU_WAIT_TAIL]],
    		   ".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]);
    #ifdef CONFIG_RCU_BOOST
    	seq_printf(m, ",%d,\"%c\"",
    		   per_cpu(rcu_cpu_has_work, rdp->cpu),
    		   convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
    					  rdp->cpu)));
    #endif /* #ifdef CONFIG_RCU_BOOST */
    	seq_printf(m, ",%ld", rdp->blimit);
    	seq_printf(m, ",%lu,%lu,%lu\n",
    		   rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
    }
    
    static int show_rcudata_csv(struct seq_file *m, void *unused)
    {
    	seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
    	seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
    	seq_puts(m, "\"of\",\"qll\",\"ql\",\"qs\"");
    #ifdef CONFIG_RCU_BOOST
    	seq_puts(m, "\"kt\",\"ktl\"");
    #endif /* #ifdef CONFIG_RCU_BOOST */
    	seq_puts(m, ",\"b\",\"ci\",\"co\",\"ca\"\n");
    #ifdef CONFIG_TREE_PREEMPT_RCU
    	seq_puts(m, "\"rcu_preempt:\"\n");
    	PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data_csv, m);
    #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
    	seq_puts(m, "\"rcu_sched:\"\n");
    	PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data_csv, m);
    	seq_puts(m, "\"rcu_bh:\"\n");
    	PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data_csv, m);
    	return 0;
    }
    
    static int rcudata_csv_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcudata_csv, NULL);
    }
    
    static const struct file_operations rcudata_csv_fops = {
    	.owner = THIS_MODULE,
    	.open = rcudata_csv_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    #ifdef CONFIG_RCU_BOOST
    
    static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
    {
    	seq_printf(m,  "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu "
    		   "j=%04x bt=%04x\n",
    		   rnp->grplo, rnp->grphi,
    		   "T."[list_empty(&rnp->blkd_tasks)],
    		   "N."[!rnp->gp_tasks],
    		   "E."[!rnp->exp_tasks],
    		   "B."[!rnp->boost_tasks],
    		   convert_kthread_status(rnp->boost_kthread_status),
    		   rnp->n_tasks_boosted, rnp->n_exp_boosts,
    		   rnp->n_normal_boosts,
    		   (int)(jiffies & 0xffff),
    		   (int)(rnp->boost_time & 0xffff));
    	seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n",
    		   "     balk",
    		   rnp->n_balk_blkd_tasks,
    		   rnp->n_balk_exp_gp_tasks,
    		   rnp->n_balk_boost_tasks,
    		   rnp->n_balk_notblocked,
    		   rnp->n_balk_notyet,
    		   rnp->n_balk_nos);
    }
    
    static int show_rcu_node_boost(struct seq_file *m, void *unused)
    {
    	struct rcu_node *rnp;
    
    	rcu_for_each_leaf_node(&rcu_preempt_state, rnp)
    		print_one_rcu_node_boost(m, rnp);
    	return 0;
    }
    
    static int rcu_node_boost_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcu_node_boost, NULL);
    }
    
    static const struct file_operations rcu_node_boost_fops = {
    	.owner = THIS_MODULE,
    	.open = rcu_node_boost_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    /*
     * Create the rcuboost debugfs entry.  Standard error return.
     */
    static int rcu_boost_trace_create_file(struct dentry *rcudir)
    {
    	return !debugfs_create_file("rcuboost", 0444, rcudir, NULL,
    				    &rcu_node_boost_fops);
    }
    
    #else /* #ifdef CONFIG_RCU_BOOST */
    
    static int rcu_boost_trace_create_file(struct dentry *rcudir)
    {
    	return 0;  /* There cannot be an error if we didn't create it! */
    }
    
    #endif /* #else #ifdef CONFIG_RCU_BOOST */
    
    static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
    {
    	unsigned long gpnum;
    	int level = 0;
    	struct rcu_node *rnp;
    
    	gpnum = rsp->gpnum;
    	seq_printf(m, "c=%lu g=%lu s=%d jfq=%ld j=%x "
    		      "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu\n",
    		   rsp->completed, gpnum, rsp->fqs_state,
    		   (long)(rsp->jiffies_force_qs - jiffies),
    		   (int)(jiffies & 0xffff),
    		   rsp->n_force_qs, rsp->n_force_qs_ngp,
    		   rsp->n_force_qs - rsp->n_force_qs_ngp,
    		   rsp->n_force_qs_lh);
    	for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < NUM_RCU_NODES; rnp++) {
    		if (rnp->level != level) {
    			seq_puts(m, "\n");
    			level = rnp->level;
    		}
    		seq_printf(m, "%lx/%lx %c%c>%c %d:%d ^%d    ",
    			   rnp->qsmask, rnp->qsmaskinit,
    			   ".G"[rnp->gp_tasks != NULL],
    			   ".E"[rnp->exp_tasks != NULL],
    			   ".T"[!list_empty(&rnp->blkd_tasks)],
    			   rnp->grplo, rnp->grphi, rnp->grpnum);
    	}
    	seq_puts(m, "\n");
    }
    
    static int show_rcuhier(struct seq_file *m, void *unused)
    {
    #ifdef CONFIG_TREE_PREEMPT_RCU
    	seq_puts(m, "rcu_preempt:\n");
    	print_one_rcu_state(m, &rcu_preempt_state);
    #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
    	seq_puts(m, "rcu_sched:\n");
    	print_one_rcu_state(m, &rcu_sched_state);
    	seq_puts(m, "rcu_bh:\n");
    	print_one_rcu_state(m, &rcu_bh_state);
    	return 0;
    }
    
    static int rcuhier_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcuhier, NULL);
    }
    
    static const struct file_operations rcuhier_fops = {
    	.owner = THIS_MODULE,
    	.open = rcuhier_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp)
    {
    	unsigned long flags;
    	unsigned long completed;
    	unsigned long gpnum;
    	unsigned long gpage;
    	unsigned long gpmax;
    	struct rcu_node *rnp = &rsp->node[0];
    
    	raw_spin_lock_irqsave(&rnp->lock, flags);
    	completed = rsp->completed;
    	gpnum = rsp->gpnum;
    	if (rsp->completed == rsp->gpnum)
    		gpage = 0;
    	else
    		gpage = jiffies - rsp->gp_start;
    	gpmax = rsp->gp_max;
    	raw_spin_unlock_irqrestore(&rnp->lock, flags);
    	seq_printf(m, "%s: completed=%ld  gpnum=%lu  age=%ld  max=%ld\n",
    		   rsp->name, completed, gpnum, gpage, gpmax);
    }
    
    static int show_rcugp(struct seq_file *m, void *unused)
    {
    #ifdef CONFIG_TREE_PREEMPT_RCU
    	show_one_rcugp(m, &rcu_preempt_state);
    #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
    	show_one_rcugp(m, &rcu_sched_state);
    	show_one_rcugp(m, &rcu_bh_state);
    	return 0;
    }
    
    static int rcugp_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcugp, NULL);
    }
    
    static const struct file_operations rcugp_fops = {
    	.owner = THIS_MODULE,
    	.open = rcugp_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
    {
    	seq_printf(m, "%3d%cnp=%ld "
    		   "qsp=%ld rpq=%ld cbr=%ld cng=%ld "
    		   "gpc=%ld gps=%ld nf=%ld nn=%ld\n",
    		   rdp->cpu,
    		   cpu_is_offline(rdp->cpu) ? '!' : ' ',
    		   rdp->n_rcu_pending,
    		   rdp->n_rp_qs_pending,
    		   rdp->n_rp_report_qs,
    		   rdp->n_rp_cb_ready,
    		   rdp->n_rp_cpu_needs_gp,
    		   rdp->n_rp_gp_completed,
    		   rdp->n_rp_gp_started,
    		   rdp->n_rp_need_fqs,
    		   rdp->n_rp_need_nothing);
    }
    
    static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
    {
    	int cpu;
    	struct rcu_data *rdp;
    
    	for_each_possible_cpu(cpu) {
    		rdp = per_cpu_ptr(rsp->rda, cpu);
    		if (rdp->beenonline)
    			print_one_rcu_pending(m, rdp);
    	}
    }
    
    static int show_rcu_pending(struct seq_file *m, void *unused)
    {
    #ifdef CONFIG_TREE_PREEMPT_RCU
    	seq_puts(m, "rcu_preempt:\n");
    	print_rcu_pendings(m, &rcu_preempt_state);
    #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
    	seq_puts(m, "rcu_sched:\n");
    	print_rcu_pendings(m, &rcu_sched_state);
    	seq_puts(m, "rcu_bh:\n");
    	print_rcu_pendings(m, &rcu_bh_state);
    	return 0;
    }
    
    static int rcu_pending_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcu_pending, NULL);
    }
    
    static const struct file_operations rcu_pending_fops = {
    	.owner = THIS_MODULE,
    	.open = rcu_pending_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    static int show_rcutorture(struct seq_file *m, void *unused)
    {
    	seq_printf(m, "rcutorture test sequence: %lu %s\n",
    		   rcutorture_testseq >> 1,
    		   (rcutorture_testseq & 0x1) ? "(test in progress)" : "");
    	seq_printf(m, "rcutorture update version number: %lu\n",
    		   rcutorture_vernum);
    	return 0;
    }
    
    static int rcutorture_open(struct inode *inode, struct file *file)
    {
    	return single_open(file, show_rcutorture, NULL);
    }
    
    static const struct file_operations rcutorture_fops = {
    	.owner = THIS_MODULE,
    	.open = rcutorture_open,
    	.read = seq_read,
    	.llseek = seq_lseek,
    	.release = single_release,
    };
    
    static struct dentry *rcudir;
    
    static int __init rcutree_trace_init(void)
    {
    	struct dentry *retval;
    
    	rcudir = debugfs_create_dir("rcu", NULL);
    	if (!rcudir)
    		goto free_out;
    
    	retval = debugfs_create_file("rcudata", 0444, rcudir,
    						NULL, &rcudata_fops);
    	if (!retval)
    		goto free_out;
    
    	retval = debugfs_create_file("rcudata.csv", 0444, rcudir,
    						NULL, &rcudata_csv_fops);
    	if (!retval)
    		goto free_out;
    
    	if (rcu_boost_trace_create_file(rcudir))
    		goto free_out;
    
    	retval = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
    	if (!retval)
    		goto free_out;
    
    	retval = debugfs_create_file("rcuhier", 0444, rcudir,
    						NULL, &rcuhier_fops);
    	if (!retval)
    		goto free_out;
    
    	retval = debugfs_create_file("rcu_pending", 0444, rcudir,
    						NULL, &rcu_pending_fops);
    	if (!retval)
    		goto free_out;
    
    	retval = debugfs_create_file("rcutorture", 0444, rcudir,
    						NULL, &rcutorture_fops);
    	if (!retval)
    		goto free_out;
    	return 0;
    free_out:
    	debugfs_remove_recursive(rcudir);
    	return 1;
    }
    
    static void __exit rcutree_trace_cleanup(void)
    {
    	debugfs_remove_recursive(rcudir);
    }
    
    
    module_init(rcutree_trace_init);
    module_exit(rcutree_trace_cleanup);
    
    MODULE_AUTHOR("Paul E. McKenney");
    MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation");
    MODULE_LICENSE("GPL");