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Date: Mon, 27 Oct 2008 16:57:48 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Lai Jiangshan <laijs@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, rjw@...k.pl,
dipankar@...ibm.com, tglx@...uxtronix.de, andi@...stfloor.org
Subject: Re: [PATCH] v3 rudimentary tracing for Classic RCU
On Mon, Oct 27, 2008 at 02:50:29PM -0700, Paul E. McKenney wrote:
> On Sun, Oct 26, 2008 at 02:59:30PM -0700, Paul E. McKenney wrote:
> > On Thu, Oct 23, 2008 at 07:12:09PM +0800, Lai Jiangshan wrote:
> > >
> > > trivial ported it to seq_file.
> > > seq_file are very good for the output buffer.
> >
> > Thank you for putting this together!!! Looks good at first glance --
> > I will test it out.
>
> So it does seem to operate correctly. I combined it with my patch and
> applied against 2.6.27 for ease of testing.
>
> One question -- why the multi-line format? This would be a bit
> awkward on a 128-CPU system, let alone on a 4,096-CPU system.
> Or am I missing some trick here?
To clarify, by "missing some trick", I am wondering if there is some
command that works in blocks of lines. After all, /proc/cpuinfo
produces the same sort of output that your patch does. ;-)
Thanx, Paul
> > > Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> > > ---
> > > diff --git a/kernel/rcuclassic_trace.c b/kernel/rcuclassic_trace.c
> > > index d19780b..f19217c
> > > --- a/kernel/rcuclassic_trace.c
> > > +++ b/kernel/rcuclassic_trace.c
> > > @@ -23,157 +23,167 @@
> > > * 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 <asm/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>
> > >
> > > -static DEFINE_MUTEX(rcuclassic_trace_mutex);
> > > -static char *rcuclassic_trace_buf;
> > > -#define RCUCLASSIC_TRACE_BUF_SIZE (128 * num_possible_cpus() + 100)
> > > +static struct rcu_data *get_rcu_data_bh(int cpu)
> > > +{
> > > + return &per_cpu(rcu_bh_data, cpu);
> > > +}
> > >
> > > -static int print_one_rcu_data(struct rcu_data *rdp, char *buf, char *ebuf)
> > > +static struct rcu_data *get_rcu_data(int cpu)
> > > {
> > > - int cnt = 0;
> > > + return &per_cpu(rcu_data, cpu);
> > > +}
> > >
> > > +static int show_rcu_data(struct seq_file *m, void *v)
> > > +{
> > > + struct rcu_data *rdp = v;
> > > if (!rdp->beenonline)
> > > return 0;
> > > - cnt += snprintf(&buf[cnt], ebuf - &buf[cnt],
> > > - "%3d%cqb=%ld b=%ld pq=%d qsp=%d ql=%ld bl=%ld\n",
> > > - rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ',
> > > - rdp->quiescbatch, rdp->batch, rdp->passed_quiesc,
> > > - rdp->qs_pending, rdp->qlen, rdp->blimit);
> > > - return cnt;
> > > +
> > > + seq_printf(m, "processor\t: %d", rdp->cpu);
> > > + if (cpu_is_offline(rdp->cpu))
> > > + seq_puts(m, "!\n");
> > > + else
> > > + seq_puts(m, "\n");
> > > + seq_printf(m, "quiescbatch\t: %ld\n", rdp->quiescbatch);
> > > + seq_printf(m, "batch\t: %ld\n", rdp->batch);
> > > + seq_printf(m, "passed_quiesc\t: %d\n", rdp->passed_quiesc);
> > > + seq_printf(m, "qs_pending\t: %d\n", rdp->qs_pending);
> > > + seq_printf(m, "qlen\t: %ld\n", rdp->qlen);
> > > + seq_printf(m, "blimit\t: %ld\n", rdp->blimit);
> > > + seq_puts(m, "\n\n");
> > > + return 0;
> > > }
> > >
> > > -#define PRINT_RCU_DATA(name, buf, ebuf) \
> > > - do { \
> > > - int _p_r_d_i; \
> > > - \
> > > - for_each_possible_cpu(_p_r_d_i) \
> > > - (buf) += print_one_rcu_data(&per_cpu(name, _p_r_d_i), \
> > > - buf, ebuf); \
> > > - } while (0)
> > > -
> > > -static ssize_t rcudata_read(struct file *filp, char __user *buffer,
> > > - size_t count, loff_t *ppos)
> > > +static void *c_start(struct seq_file *m, loff_t *pos)
> > > {
> > > - ssize_t bcount;
> > > - char *buf = rcuclassic_trace_buf;
> > > - char *ebuf = &rcuclassic_trace_buf[RCUCLASSIC_TRACE_BUF_SIZE];
> > > -
> > > - mutex_lock(&rcuclassic_trace_mutex);
> > > - buf += snprintf(buf, ebuf - buf, "rcu:\n");
> > > - PRINT_RCU_DATA(rcu_data, buf, ebuf);
> > > - buf += snprintf(buf, ebuf - buf, "rcu_bh:\n");
> > > - PRINT_RCU_DATA(rcu_bh_data, buf, ebuf);
> > > - bcount = simple_read_from_buffer(buffer, count, ppos,
> > > - rcuclassic_trace_buf, strlen(rcuclassic_trace_buf));
> > > - mutex_unlock(&rcuclassic_trace_mutex);
> > > - return bcount;
> > > + typedef struct rcu_data *(*get_data_func)(int);
> > > +
> > > + if (*pos == 0) /* just in case, cpu 0 is not the first */
> > > + *pos = first_cpu(cpu_possible_map);
> > > + else
> > > + *pos = next_cpu_nr(*pos - 1, cpu_possible_map);
> > > + if ((*pos) < nr_cpu_ids)
> > > + return ((get_data_func)m->private)(*pos);
> > > + return NULL;
> > > }
> > >
> > > -static int print_one_rcu_ctrlblk(struct rcu_ctrlblk *rcp, char *buf, char *ebuf)
> > > +static void *c_next(struct seq_file *m, void *v, loff_t *pos)
> > > {
> > > - int cnt = 0;
> > > -
> > > - cnt += snprintf(&buf[cnt], ebuf - &buf[cnt], "cur=%ld completed=%ld "
> > > - "pending=%ld s=%d\n\t",
> > > - rcp->cur, rcp->completed,
> > > - rcp->pending, rcp->signaled);
> > > - cnt += cpulist_scnprintf(&buf[cnt], ebuf - &buf[cnt], rcp->cpumask);
> > > - cnt += snprintf(&buf[cnt], ebuf - &buf[cnt], "\n");
> > > - return cnt;
> > > + (*pos)++;
> > > + return c_start(m, pos);
> > > }
> > >
> > > -static ssize_t rcucb_read(struct file *filp, char __user *buffer,
> > > - size_t count, loff_t *ppos)
> > > +static void c_stop(struct seq_file *m, void *v)
> > > {
> > > - ssize_t bcount;
> > > - char *buf = rcuclassic_trace_buf;
> > > - char *ebuf = &rcuclassic_trace_buf[RCUCLASSIC_TRACE_BUF_SIZE];
> > > -
> > > - mutex_lock(&rcuclassic_trace_mutex);
> > > - buf += snprintf(buf, ebuf - buf, "rcu: ");
> > > - buf += print_one_rcu_ctrlblk(&rcu_ctrlblk, buf, ebuf);
> > > - buf += snprintf(buf, ebuf - buf, "rcu_bh: ");
> > > - buf += print_one_rcu_ctrlblk(&rcu_bh_ctrlblk, buf, ebuf);
> > > - buf += snprintf(buf, ebuf - buf, "online: ");
> > > - buf += cpulist_scnprintf(buf, ebuf - buf, cpu_online_map);
> > > - buf += snprintf(buf, ebuf - buf, "\n");
> > > - bcount = simple_read_from_buffer(buffer, count, ppos,
> > > - rcuclassic_trace_buf, strlen(rcuclassic_trace_buf));
> > > - mutex_unlock(&rcuclassic_trace_mutex);
> > > - return bcount;
> > > }
> > >
> > > -static struct file_operations rcudata_fops = {
> > > - .owner = THIS_MODULE,
> > > - .read = rcudata_read,
> > > +const struct seq_operations rcu_data_seq_op = {
> > > + .start = c_start,
> > > + .next = c_next,
> > > + .stop = c_stop,
> > > + .show = show_rcu_data,
> > > };
> > >
> > > +static int rcu_data_open(struct inode *inode, struct file *file)
> > > +{
> > > + int ret = seq_open(file, &rcu_data_seq_op);
> > > + if (ret)
> > > + return ret;
> > > + ((struct seq_file *)file->private_data)->private = inode->i_private;
> > > + return 0;
> > > +}
> > > +
> > > +static const struct file_operations rcu_data_fops = {
> > > + .owner = THIS_MODULE,
> > > + .open = rcu_data_open,
> > > + .read = seq_read,
> > > + .llseek = seq_lseek,
> > > + .release = seq_release,
> > > +};
> > > +
> > > +static void print_one_rcu_ctrlblk(struct seq_file *m, struct rcu_ctrlblk *rcp)
> > > +{
> > > + seq_printf(m, "cur=%ld completed=%ld pending=%ld s=%d\n\t",
> > > + rcp->cur, rcp->completed, rcp->pending, rcp->signaled);
> > > + seq_cpumask(m, &rcp->cpumask);
> > > + seq_puts(m, "\n");
> > > +}
> > > +
> > > +static int show_rcucb(struct seq_file *m, void *unused)
> > > +{
> > > + seq_puts(m, "rcu: ");
> > > + print_one_rcu_ctrlblk(m, &rcu_ctrlblk);
> > > + seq_puts(m, "rcu_bh: ");
> > > + print_one_rcu_ctrlblk(m, &rcu_bh_ctrlblk);
> > > + seq_puts(m, "online: ");
> > > + seq_cpumask(m, &cpu_online_map);
> > > + seq_puts(m, "\n");
> > > + return 0;
> > > +}
> > > +
> > > +static int rcucb_open(struct inode *inode, struct file *file)
> > > +{
> > > + return single_open(file, show_rcucb, NULL);
> > > +}
> > > +
> > > static struct file_operations rcucb_fops = {
> > > - .owner = THIS_MODULE,
> > > - .read = rcucb_read,
> > > + .owner = THIS_MODULE,
> > > + .open = rcucb_open,
> > > + .read = seq_read,
> > > + .llseek = seq_lseek,
> > > + .release = single_release,
> > > };
> > >
> > > -static struct dentry *rcudir, *datadir, *cbdir;
> > > -static int rcuclassic_debugfs_init(void)
> > > +static struct dentry *rcudir, *rcu_bh_data_file, *rcu_data_file, *rcucb_file;
> > > +
> > > +static int __init rcuclassic_trace_init(void)
> > > {
> > > rcudir = debugfs_create_dir("rcu", NULL);
> > > if (!rcudir)
> > > goto out;
> > > - datadir = debugfs_create_file("rcudata", 0444, rcudir,
> > > - NULL, &rcudata_fops);
> > > - if (!datadir)
> > > - goto free_out;
> > > - cbdir = debugfs_create_file("rcucb", 0444, rcudir, NULL, &rcucb_fops);
> > > - if (!cbdir)
> > > - goto free_out;
> > > +
> > > + rcu_bh_data_file = debugfs_create_file("rcu_bh_data", 0444, rcudir,
> > > + get_rcu_data_bh, &rcu_data_fops);
> > > + if (!rcu_bh_data_file)
> > > + goto out_rcudir;
> > > +
> > > + rcu_data_file = debugfs_create_file("rcu_data", 0444, rcudir,
> > > + get_rcu_data, &rcu_data_fops);
> > > + if (!rcu_data_file)
> > > + goto out_rcudata_bh_file;
> > > +
> > > + rcucb_file = debugfs_create_file("rcucb", 0444, rcudir,
> > > + NULL, &rcucb_fops);
> > > + if (!rcucb_file)
> > > + goto out_rcudata_file;
> > > return 0;
> > > -free_out:
> > > - if (datadir)
> > > - debugfs_remove(datadir);
> > > +
> > > +out_rcudata_file:
> > > + debugfs_remove(rcu_data_file);
> > > +out_rcudata_bh_file:
> > > + debugfs_remove(rcu_bh_data_file);
> > > +out_rcudir:
> > > debugfs_remove(rcudir);
> > > out:
> > > return 1;
> > > }
> > >
> > > -static int __init rcuclassic_trace_init(void)
> > > -{
> > > - int ret;
> > > -
> > > - rcuclassic_trace_buf = kmalloc(RCUCLASSIC_TRACE_BUF_SIZE, GFP_KERNEL);
> > > - if (!rcuclassic_trace_buf)
> > > - return 1;
> > > - ret = rcuclassic_debugfs_init();
> > > - if (ret)
> > > - kfree(rcuclassic_trace_buf);
> > > - return ret;
> > > -}
> > > -
> > > static void __exit rcuclassic_trace_cleanup(void)
> > > {
> > > - debugfs_remove(datadir);
> > > - debugfs_remove(cbdir);
> > > + debugfs_remove(rcucb_file);
> > > + debugfs_remove(rcu_data_file);
> > > + debugfs_remove(rcu_bh_data_file);
> > > debugfs_remove(rcudir);
> > > - kfree(rcuclassic_trace_buf);
> > > }
> > >
> > > -
> > > module_init(rcuclassic_trace_init);
> > > module_exit(rcuclassic_trace_cleanup);
> > > +
> > > +MODULE_AUTHOR("Paul E. McKenney");
> > > +MODULE_DESCRIPTION("Read-Copy Update tracing for classic implementation");
> > > +MODULE_LICENSE("GPL");
> > >
--
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