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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-04-13 21:31:17 -0700
committerIngo Molnar <mingo@elte.hu>2009-04-14 11:33:43 +0200
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)
check_cpu_stall(rsp, rdp);
/* Is the RCU core waiting for a quiescent state from this CPU? */
- if (rdp->qs_pending)
+ if (rdp->qs_pending) {
+ rdp->n_rp_qs_pending++;
return 1;
+ }
/* Does this CPU have callbacks ready to invoke? */
- if (cpu_has_callbacks_ready_to_invoke(rdp))
+ if (cpu_has_callbacks_ready_to_invoke(rdp)) {
+ rdp->n_rp_cb_ready++;
return 1;
+ }
/* Has RCU gone idle with this CPU needing another grace period? */
- if (cpu_needs_another_gp(rsp, rdp))
+ if (cpu_needs_another_gp(rsp, rdp)) {
+ rdp->n_rp_cpu_needs_gp++;
return 1;
+ }
/* Has another RCU grace period completed? */
- if (ACCESS_ONCE(rsp->completed) != rdp->completed) /* outside of lock */
+ if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */
+ rdp->n_rp_gp_completed++;
return 1;
+ }
/* Has a new RCU grace period started? */
- if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) /* outside of lock */
+ if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */
+ rdp->n_rp_gp_started++;
return 1;
+ }
/* Has an RCU GP gone long enough to send resched IPIs &c? */
if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) &&
- ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0))
+ ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) {
+ rdp->n_rp_need_fqs++;
return 1;
+ }
/* nothing to do */
+ rdp->n_rp_need_nothing++;
return 0;
}
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 = {
.release = single_release,
};
-static struct dentry *rcudir, *datadir, *datadir_csv, *hierdir, *gpdir;
+static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
+{
+ seq_printf(m, "%3d%cnp=%ld "
+ "qsp=%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_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 = rsp->rda[cpu];
+ if (rdp->beenonline)
+ print_one_rcu_pending(m, rdp);
+ }
+}
+
+static int show_rcu_pending(struct seq_file *m, void *unused)
+{
+ seq_puts(m, "rcu:\n");
+ print_rcu_pendings(m, &rcu_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 struct file_operations rcu_pending_fops = {
+ .owner = THIS_MODULE,
+ .open = rcu_pending_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static struct dentry *rcudir;
+static struct dentry *datadir;
+static struct dentry *datadir_csv;
+static struct dentry *gpdir;
+static struct dentry *hierdir;
+static struct dentry *rcu_pendingdir;
+
static int __init rcuclassic_trace_init(void)
{
rcudir = debugfs_create_dir("rcu", NULL);
@@ -238,6 +294,11 @@ static int __init rcuclassic_trace_init(void)
NULL, &rcuhier_fops);
if (!hierdir)
goto free_out;
+
+ rcu_pendingdir = debugfs_create_file("rcu_pending", 0444, rcudir,
+ NULL, &rcu_pending_fops);
+ if (!rcu_pendingdir)
+ goto free_out;
return 0;
free_out:
if (datadir)
@@ -257,6 +318,7 @@ static void __exit rcuclassic_trace_cleanup(void)
debugfs_remove(datadir_csv);
debugfs_remove(gpdir);
debugfs_remove(hierdir);
+ debugfs_remove(rcu_pendingdir);
debugfs_remove(rcudir);
}