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Message-Id: <1361921596-9636-3-git-send-email-nzimmer@sgi.com>
Date: Tue, 26 Feb 2013 17:33:16 -0600
From: Nathan Zimmer <nzimmer@....com>
To: unlisted-recipients:; (no To-header on input)
Cc: johnstul@...ibm.com, tglx@...utronix.de, sboyd@...eaurora.org,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
Nathan Zimmer <nzimmer@....com>
Subject: [PATCH v3 2/2] 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.
Signed-off-by: Nathan Zimmer <nzimmer@....com>
Reported-by: Dave Jones <davej@...hat.com>
Cc: John Stultz <johnstul@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Stephen Boyd <sboyd@...eaurora.org>
v2: Added comments on the iteration and other fixups pointed to by Andrew.
v3: Corrected the case where max_cpus != nr_cpu_ids by exiting early.
---
kernel/time/timer_list.c | 99 ++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 87 insertions(+), 12 deletions(-)
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index b3dc3d6..ee0bb5e 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -253,38 +253,113 @@ static int timer_list_show(struct seq_file *m, void *v)
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");
-
- for_each_online_cpu(cpu)
+ if (v == (void *)1) {
+ 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");
+ } else if (v < (void *)(unsigned long)(nr_cpu_ids + 2)) {
+ cpu = (unsigned long)(v - 2);
print_cpu(m, cpu, now);
-
+ }
#ifdef CONFIG_GENERIC_CLOCKEVENTS
- timer_list_show_tickdevices_header(m);
- for_each_online_cpu(cpu)
+ else if (v == (void *)(unsigned long)nr_cpu_ids + 2) {
+ timer_list_show_tickdevices_header(m);
+ } else {
+ cpu = (unsigned long)(v - 3 - nr_cpu_ids);
print_tickdevice(m, tick_get_device(cpu), cpu);
+ }
#endif
-
return 0;
}
+/*
+ * This itererator really needs some explanation since it is offset and has
+ * two passes, one of which is controlled by a config option.
+ * In a hotpluggable systems some cpus, including cpu 0 and the last cpu, may
+ * be missing so we have to use cpumask_* to iterate over the cpus.
+ * For the first pass:
+ * It returns 1 for the header position.
+ * For cpu 0 it returns 2 and the final possible cpu would be nr_cpu_ids + 1.
+ * On the second pass:
+ * It returnes nr_cpu_ids + 1 for the second header position.
+ * For cpu 0 it returns nr_cpu_ids + 2
+ * The final possible cpu would be nr_cpu_ids + nr_cpu_ids + 2.
+ * It is also important to remember that cpumask_next returns >= nr_cpu_ids if
+ * no further cpus set.
+ */
+static void *timer_list_start(struct seq_file *file, loff_t *offset)
+{
+ unsigned long n = *offset;
+
+ if (n == 0)
+ return (void *) 1;
+
+ if (n < nr_cpu_ids + 1) {
+ n = cpumask_next(n - 2, cpu_online_mask);
+ if (n >= nr_cpu_ids)
+ n = nr_cpu_ids;
+ *offset = n + 1;
+ return (void *)(unsigned long)(n + 2);
+ }
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+ if (n == nr_cpu_ids + 1)
+ return (void *)(unsigned long)(nr_cpu_ids + 2);
+
+ if (n < nr_cpu_ids * 2 + 2) {
+ n -= (nr_cpu_ids + 2);
+ n = cpumask_next(n - 1, cpu_online_mask);
+ if (n >= nr_cpu_ids)
+ return NULL;
+ *offset = n + 2 + nr_cpu_ids;
+ return (void *)(unsigned long)(n + 3 + nr_cpu_ids);
+ }
+#endif
+
+ return NULL;
+}
+
+static void *timer_list_next(struct seq_file *file, void *data, loff_t *offset)
+{
+ (*offset)++;
+ return timer_list_start(file, offset);
+}
+
+static void timer_list_stop(struct seq_file *file, void *data)
+{
+}
+
+static const struct seq_operations timer_list_sops = {
+ .start = timer_list_start,
+ .next = timer_list_next,
+ .stop = timer_list_stop,
+ .show = timer_list_show,
+};
+
void sysrq_timer_list_show(void)
{
timer_list_show(NULL, NULL);
}
+static int timer_list_release(struct inode *inode, struct file *filep)
+{
+ seq_release(inode, filep);
+
+ return 0;
+}
+
static int timer_list_open(struct inode *inode, struct file *filp)
{
- return single_open(filp, timer_list_show, NULL);
+ return seq_open(filp, &timer_list_sops);
}
static const struct file_operations timer_list_fops = {
.open = timer_list_open,
.read = seq_read,
.llseek = seq_lseek,
- .release = single_release,
+ .release = timer_list_release,
};
static int __init init_timer_list_procfs(void)
--
1.8.1.2
--
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