timer_list: Convert timer list to be a proper seq_file

When running with 4096 cores attemping to read /proc/timer_list will fail
with an ENOMEM condition.  On a sufficantly large systems the total amount
of data is more then 4mb, so it won't fit into a single buffer.  The
failure can also occur on smaller systems when memory fragmentation is
high as reported by Dave Jones.

Convert /proc/timer_list to a proper seq_file with its own iterator.  This
is a little more complex given that we have to make two passes with two
separate headers.

sysrq_timer_list_show also needed to be updated to reflect the fact that
now timer_list_show only does one cpu at at time.

Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Reported-by: Dave Jones <davej@redhat.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Link: http://lkml.kernel.org/r/1364345790-14577-3-git-send-email-nzimmer@sgi.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 380a589..3bdf283 100644 (file)
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -20,6 +20,13 @@
 
 #include <asm/uaccess.h>
 
+
+struct timer_list_iter {
+       int cpu;
+       bool second_pass;
+       u64 now;
+};
+
 typedef void (*print_fn_t)(struct seq_file *m, unsigned int *classes);
 
 DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
@@ -247,43 +254,101 @@ static void timer_list_show_tickdevices_header(struct seq_file *m)
 }
 #endif
 
-static int timer_list_show(struct seq_file *m, void *v)
+static inline void timer_list_header(struct seq_file *m, u64 now)
 {
-       u64 now = ktime_to_ns(ktime_get());
-       int cpu;
-
        SEQ_printf(m, "Timer List Version: v0.7\n");
        SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
        SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
        SEQ_printf(m, "\n");
+}
+
+static int timer_list_show(struct seq_file *m, void *v)
+{
+       struct timer_list_iter *iter = v;
+       u64 now = ktime_to_ns(ktime_get());
+
+       if (iter->cpu == -1 && !iter->second_pass)
+               timer_list_header(m, now);
+       else if (!iter->second_pass)
+               print_cpu(m, iter->cpu, iter->now);
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+       else if (iter->cpu == -1 && iter->second_pass)
+               timer_list_show_tickdevices_header(m);
+       else
+               print_tickdevice(m, tick_get_device(iter->cpu), iter->cpu);
+#endif
+       return 0;
+}
+
+void sysrq_timer_list_show(void)
+{
+       u64 now = ktime_to_ns(ktime_get());
+       int cpu;
+
+       timer_list_header(NULL, now);
 
        for_each_online_cpu(cpu)
-               print_cpu(m, cpu, now);
+               print_cpu(NULL, cpu, now);
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
-       timer_list_show_tickdevices_header(m);
+       timer_list_show_tickdevices_header(NULL);
        for_each_online_cpu(cpu)
-               print_tickdevice(m, tick_get_device(cpu), cpu);
+               print_tickdevice(NULL, tick_get_device(cpu), cpu);
 #endif
+       return;
+}
 
-       return 0;
+static void *timer_list_start(struct seq_file *file, loff_t *offset)
+{
+       struct timer_list_iter *iter = file->private;
+
+       if (!*offset) {
+               iter->cpu = -1;
+               iter->now = ktime_to_ns(ktime_get());
+       } else if (iter->cpu >= nr_cpu_ids) {
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+               if (!iter->second_pass) {
+                       iter->cpu = -1;
+                       iter->second_pass = true;
+               } else
+                       return NULL;
+#else
+               return NULL;
+#endif
+       }
+       return iter;
 }
 
-void sysrq_timer_list_show(void)
+static void *timer_list_next(struct seq_file *file, void *v, loff_t *offset)
 {
-       timer_list_show(NULL, NULL);
+       struct timer_list_iter *iter = file->private;
+       iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
+       ++*offset;
+       return timer_list_start(file, offset);
 }
 
+static void timer_list_stop(struct seq_file *seq, void *v)
+{
+}
+
+static const struct seq_operations timer_list_sops = {
+       .start = timer_list_start,
+       .next = timer_list_next,
+       .stop = timer_list_stop,
+       .show = timer_list_show,
+};
+
 static int timer_list_open(struct inode *inode, struct file *filp)
 {
-       return single_open(filp, timer_list_show, NULL);
+       return seq_open_private(filp, &timer_list_sops,
+                       sizeof(struct timer_list_iter));
 }
 
 static const struct file_operations timer_list_fops = {
        .open           = timer_list_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
-       .release        = single_release,
+       .release        = seq_release_private,
 };
 
 static int __init init_timer_list_procfs(void)