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    SubjectRe: [PATCH] v3 rudimentary tracing for Classic RCU
    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.

    Thanx, Paul

    > Signed-off-by: Lai Jiangshan <laijs@cn.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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