Messages in this thread Patch in this message | | | From | Nathan Zimmer <> | Subject | [PATCH v3 2/2] timer_list: convert timer list to be a proper seq_file | Date | Tue, 26 Feb 2013 17:33:16 -0600 |
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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@sgi.com> Reported-by: Dave Jones <davej@redhat.com> Cc: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@codeaurora.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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