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Commit f763cf8e authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'ras-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull RAS fixes from Thomas Gleixner:
 "Two small fixes for RAS:

   - Use a proper search algorithm to find the correct element in the
     CEC array. The replacement was a better choice than fixing the
     crash causes by the original search function with horrible duct
     tape.

   - Move the timer based decay function into thread context so it can
     actually acquire the mutex which protects the CEC array to prevent
     corruption"

* 'ras-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  RAS/CEC: Convert the timer callback to a workqueue
  RAS/CEC: Fix binary search function
parents e01e060f 0ade0b62

drivers/ras/cec.c

+42 −38
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/mm.h>

#include <linux/gfp.h>

#include <linux/kernel.h>

#include <linux/workqueue.h>



#include <asm/mce.h>
@@ -123,16 +124,12 @@ static u64 dfs_pfn; 
/* Amount of errors after which we offline */

static unsigned int count_threshold = COUNT_MASK;



/*

 * The timer "decays" element count each timer_interval which is 24hrs by

 * default.

 */



#define CEC_TIMER_DEFAULT_INTERVAL	24 * 60 * 60	/* 24 hrs */

#define CEC_TIMER_MIN_INTERVAL		 1 * 60 * 60	/* 1h */

#define CEC_TIMER_MAX_INTERVAL	   30 *	24 * 60 * 60	/* one month */

static struct timer_list cec_timer;

static u64 timer_interval = CEC_TIMER_DEFAULT_INTERVAL;

/* Each element "decays" each decay_interval which is 24hrs by default. */

#define CEC_DECAY_DEFAULT_INTERVAL	24 * 60 * 60	/* 24 hrs */

#define CEC_DECAY_MIN_INTERVAL		 1 * 60 * 60	/* 1h */

#define CEC_DECAY_MAX_INTERVAL	   30 *	24 * 60 * 60	/* one month */

static struct delayed_work cec_work;

static u64 decay_interval = CEC_DECAY_DEFAULT_INTERVAL;



/*

 * Decrement decay value. We're using DECAY_BITS bits to denote decay of an
@@ -160,20 +157,21 @@ static void do_spring_cleaning(struct ce_array *ca) 
/*

 * @interval in seconds

 */

static void cec_mod_timer(struct timer_list *t, unsigned long interval)

static void cec_mod_work(unsigned long interval)

{

	unsigned long iv;



	iv = interval * HZ + jiffies;



	mod_timer(t, round_jiffies(iv));

	iv = interval * HZ;

	mod_delayed_work(system_wq, &cec_work, round_jiffies(iv));

}



static void cec_timer_fn(struct timer_list *unused)

static void cec_work_fn(struct work_struct *work)

{

	mutex_lock(&ce_mutex);

	do_spring_cleaning(&ce_arr);

	mutex_unlock(&ce_mutex);



	cec_mod_timer(&cec_timer, timer_interval);

	cec_mod_work(decay_interval);

}



/*
@@ -183,32 +181,38 @@ static void cec_timer_fn(struct timer_list *unused) 
 */

static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to)

{

	int min = 0, max = ca->n - 1;

	u64 this_pfn;

	int min = 0, max = ca->n;



	while (min < max) {

		int tmp = (max + min) >> 1;

	while (min <= max) {

		int i = (min + max) >> 1;



		this_pfn = PFN(ca->array[tmp]);

		this_pfn = PFN(ca->array[i]);



		if (this_pfn < pfn)

			min = tmp + 1;

			min = i + 1;

		else if (this_pfn > pfn)

			max = tmp;

		else {

			min = tmp;

			break;

			max = i - 1;

		else if (this_pfn == pfn) {

			if (to)

				*to = i;



			return i;

		}

	}



	/*

	 * When the loop terminates without finding @pfn, min has the index of

	 * the element slot where the new @pfn should be inserted. The loop

	 * terminates when min > max, which means the min index points to the

	 * bigger element while the max index to the smaller element, in-between

	 * which the new @pfn belongs to.

	 *

	 * For more details, see exercise 1, Section 6.2.1 in TAOCP, vol. 3.

	 */

	if (to)

		*to = min;



	this_pfn = PFN(ca->array[min]);



	if (this_pfn == pfn)

		return min;



	return -ENOKEY;

}
@@ -374,15 +378,15 @@ static int decay_interval_set(void *data, u64 val) 
{

	*(u64 *)data = val;



	if (val < CEC_TIMER_MIN_INTERVAL)

	if (val < CEC_DECAY_MIN_INTERVAL)

		return -EINVAL;



	if (val > CEC_TIMER_MAX_INTERVAL)

	if (val > CEC_DECAY_MAX_INTERVAL)

		return -EINVAL;



	timer_interval = val;

	decay_interval = val;



	cec_mod_timer(&cec_timer, timer_interval);

	cec_mod_work(decay_interval);

	return 0;

}

DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");
@@ -426,7 +430,7 @@ static int array_dump(struct seq_file *m, void *v) 


	seq_printf(m, "Flags: 0x%x\n", ca->flags);



	seq_printf(m, "Timer interval: %lld seconds\n", timer_interval);

	seq_printf(m, "Decay interval: %lld seconds\n", decay_interval);

	seq_printf(m, "Decays: %lld\n", ca->decays_done);



	seq_printf(m, "Action threshold: %d\n", count_threshold);
@@ -472,7 +476,7 @@ static int __init create_debugfs_nodes(void) 
	}



	decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,

				    &timer_interval, &decay_interval_ops);

				    &decay_interval, &decay_interval_ops);

	if (!decay) {

		pr_warn("Error creating decay_interval debugfs node!\n");

		goto err;
@@ -508,8 +512,8 @@ void __init cec_init(void) 
	if (create_debugfs_nodes())

		return;



	timer_setup(&cec_timer, cec_timer_fn, 0);

	cec_mod_timer(&cec_timer, CEC_TIMER_DEFAULT_INTERVAL);

	INIT_DELAYED_WORK(&cec_work, cec_work_fn);

	schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL);



	pr_info("Correctable Errors collector initialized.\n");

}