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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-04-14 00:31:17 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-14 05:33:43 -0400
commit7ba5c840e64d4a967379f1ae3eca73278180b11d (patch)
treeb77d70ce2b80f3be27add39fcd3bc7fbfe7a0847 /kernel
parent05cfbd66d07c44865983c8b65ae9d0037d874206 (diff)
rcu: Add __rcu_pending tracing to hierarchical RCU
Add tracing to __rcu_pending() to provide information on why RCU processing was kicked off. This is helpful for debugging hierarchical RCU, and might also be helpful in learning how hierarchical RCU operates. Located-by: Anton Blanchard <anton@au1.ibm.com> Tested-by: Anton Blanchard <anton@au1.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: anton@samba.org Cc: akpm@linux-foundation.org Cc: dipankar@in.ibm.com Cc: manfred@colorfullife.com Cc: cl@linux-foundation.org Cc: josht@linux.vnet.ibm.com Cc: schamp@sgi.com Cc: niv@us.ibm.com Cc: dvhltc@us.ibm.com Cc: ego@in.ibm.com Cc: laijs@cn.fujitsu.com Cc: rostedt@goodmis.org Cc: peterz@infradead.org Cc: penberg@cs.helsinki.fi Cc: andi@firstfloor.org Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> LKML-Reference: <1239683479943-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcutree.c25
-rw-r--r--kernel/rcutree_trace.c64
2 files changed, 82 insertions, 7 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d2a372fb0b9b..0dccfbba6d26 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1259,31 +1259,44 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
1259 check_cpu_stall(rsp, rdp); 1259 check_cpu_stall(rsp, rdp);
1260 1260
1261 /* Is the RCU core waiting for a quiescent state from this CPU? */ 1261 /* Is the RCU core waiting for a quiescent state from this CPU? */
1262 if (rdp->qs_pending) 1262 if (rdp->qs_pending) {
1263 rdp->n_rp_qs_pending++;
1263 return 1; 1264 return 1;
1265 }
1264 1266
1265 /* Does this CPU have callbacks ready to invoke? */ 1267 /* Does this CPU have callbacks ready to invoke? */
1266 if (cpu_has_callbacks_ready_to_invoke(rdp)) 1268 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
1269 rdp->n_rp_cb_ready++;
1267 return 1; 1270 return 1;
1271 }
1268 1272
1269 /* Has RCU gone idle with this CPU needing another grace period? */ 1273 /* Has RCU gone idle with this CPU needing another grace period? */
1270 if (cpu_needs_another_gp(rsp, rdp)) 1274 if (cpu_needs_another_gp(rsp, rdp)) {
1275 rdp->n_rp_cpu_needs_gp++;
1271 return 1; 1276 return 1;
1277 }
1272 1278
1273 /* Has another RCU grace period completed? */ 1279 /* Has another RCU grace period completed? */
1274 if (ACCESS_ONCE(rsp->completed) != rdp->completed) /* outside of lock */ 1280 if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */
1281 rdp->n_rp_gp_completed++;
1275 return 1; 1282 return 1;
1283 }
1276 1284
1277 /* Has a new RCU grace period started? */ 1285 /* Has a new RCU grace period started? */
1278 if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) /* outside of lock */ 1286 if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */
1287 rdp->n_rp_gp_started++;
1279 return 1; 1288 return 1;
1289 }
1280 1290
1281 /* Has an RCU GP gone long enough to send resched IPIs &c? */ 1291 /* Has an RCU GP gone long enough to send resched IPIs &c? */
1282 if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) && 1292 if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) &&
1283 ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) 1293 ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) {
1294 rdp->n_rp_need_fqs++;
1284 return 1; 1295 return 1;
1296 }
1285 1297
1286 /* nothing to do */ 1298 /* nothing to do */
1299 rdp->n_rp_need_nothing++;
1287 return 0; 1300 return 0;
1288} 1301}
1289 1302
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 4b1875ba9404..fe1dcdbf1ca3 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -213,7 +213,63 @@ static struct file_operations rcugp_fops = {
213 .release = single_release, 213 .release = single_release,
214}; 214};
215 215
216static struct dentry *rcudir, *datadir, *datadir_csv, *hierdir, *gpdir; 216static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
217{
218 seq_printf(m, "%3d%cnp=%ld "
219 "qsp=%ld cbr=%ld cng=%ld gpc=%ld gps=%ld nf=%ld nn=%ld\n",
220 rdp->cpu,
221 cpu_is_offline(rdp->cpu) ? '!' : ' ',
222 rdp->n_rcu_pending,
223 rdp->n_rp_qs_pending,
224 rdp->n_rp_cb_ready,
225 rdp->n_rp_cpu_needs_gp,
226 rdp->n_rp_gp_completed,
227 rdp->n_rp_gp_started,
228 rdp->n_rp_need_fqs,
229 rdp->n_rp_need_nothing);
230}
231
232static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
233{
234 int cpu;
235 struct rcu_data *rdp;
236
237 for_each_possible_cpu(cpu) {
238 rdp = rsp->rda[cpu];
239 if (rdp->beenonline)
240 print_one_rcu_pending(m, rdp);
241 }
242}
243
244static int show_rcu_pending(struct seq_file *m, void *unused)
245{
246 seq_puts(m, "rcu:\n");
247 print_rcu_pendings(m, &rcu_state);
248 seq_puts(m, "rcu_bh:\n");
249 print_rcu_pendings(m, &rcu_bh_state);
250 return 0;
251}
252
253static int rcu_pending_open(struct inode *inode, struct file *file)
254{
255 return single_open(file, show_rcu_pending, NULL);
256}
257
258static struct file_operations rcu_pending_fops = {
259 .owner = THIS_MODULE,
260 .open = rcu_pending_open,
261 .read = seq_read,
262 .llseek = seq_lseek,
263 .release = single_release,
264};
265
266static struct dentry *rcudir;
267static struct dentry *datadir;
268static struct dentry *datadir_csv;
269static struct dentry *gpdir;
270static struct dentry *hierdir;
271static struct dentry *rcu_pendingdir;
272
217static int __init rcuclassic_trace_init(void) 273static int __init rcuclassic_trace_init(void)
218{ 274{
219 rcudir = debugfs_create_dir("rcu", NULL); 275 rcudir = debugfs_create_dir("rcu", NULL);
@@ -238,6 +294,11 @@ static int __init rcuclassic_trace_init(void)
238 NULL, &rcuhier_fops); 294 NULL, &rcuhier_fops);
239 if (!hierdir) 295 if (!hierdir)
240 goto free_out; 296 goto free_out;
297
298 rcu_pendingdir = debugfs_create_file("rcu_pending", 0444, rcudir,
299 NULL, &rcu_pending_fops);
300 if (!rcu_pendingdir)
301 goto free_out;
241 return 0; 302 return 0;
242free_out: 303free_out:
243 if (datadir) 304 if (datadir)
@@ -257,6 +318,7 @@ static void __exit rcuclassic_trace_cleanup(void)
257 debugfs_remove(datadir_csv); 318 debugfs_remove(datadir_csv);
258 debugfs_remove(gpdir); 319 debugfs_remove(gpdir);
259 debugfs_remove(hierdir); 320 debugfs_remove(hierdir);
321 debugfs_remove(rcu_pendingdir);
260 debugfs_remove(rcudir); 322 debugfs_remove(rcudir);
261} 323}
262 324