* [Xen-devel] [PATCH v2] timers: limit heap size
@ 2019-06-05 6:51 Jan Beulich
0 siblings, 0 replies; only message in thread
From: Jan Beulich @ 2019-06-05 6:51 UTC (permalink / raw)
To: xen-devel
Cc: Stefano Stabellini, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Ian Jackson, Tim Deegan,
Julien Grall
First and foremost make timer_softirq_action() avoid growing the heap
if its new size can't be stored without truncation. 64k entries is a
lot, and I don't think we're at risk of actually running into the issue,
but I also think it's better not to allow for hard to debug problems to
occur in the first place.
Furthermore also adjust the code such the size/limit fields becoming
unsigned int would at least work from a mere sizing point of view. For
this also switch various uses of plain int to unsigned int.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: Log (once) when heap limit would have been exceeded.
--- a/xen/common/timer.c
+++ b/xen/common/timer.c
@@ -63,9 +63,9 @@ static struct heap_metadata *heap_metada
}
/* Sink down element @pos of @heap. */
-static void down_heap(struct timer **heap, int pos)
+static void down_heap(struct timer **heap, unsigned int pos)
{
- int sz = heap_metadata(heap)->size, nxt;
+ unsigned int sz = heap_metadata(heap)->size, nxt;
struct timer *t = heap[pos];
while ( (nxt = (pos << 1)) <= sz )
@@ -84,7 +84,7 @@ static void down_heap(struct timer **hea
}
/* Float element @pos up @heap. */
-static void up_heap(struct timer **heap, int pos)
+static void up_heap(struct timer **heap, unsigned int pos)
{
struct timer *t = heap[pos];
@@ -103,8 +103,8 @@ static void up_heap(struct timer **heap,
/* Delete @t from @heap. Return TRUE if new top of heap. */
static int remove_from_heap(struct timer **heap, struct timer *t)
{
- int sz = heap_metadata(heap)->size;
- int pos = t->heap_offset;
+ unsigned int sz = heap_metadata(heap)->size;
+ unsigned int pos = t->heap_offset;
if ( unlikely(pos == sz) )
{
@@ -130,7 +130,7 @@ static int remove_from_heap(struct timer
/* Add new entry @t to @heap. Return TRUE if new top of heap. */
static int add_to_heap(struct timer **heap, struct timer *t)
{
- int sz = heap_metadata(heap)->size;
+ unsigned int sz = heap_metadata(heap)->size;
/* Fail if the heap is full. */
if ( unlikely(sz == heap_metadata(heap)->limit) )
@@ -463,9 +463,17 @@ static void timer_softirq_action(void)
if ( unlikely(ts->list != NULL) )
{
/* old_limit == (2^n)-1; new_limit == (2^(n+4))-1 */
- int old_limit = heap_metadata(heap)->limit;
- int new_limit = ((old_limit + 1) << 4) - 1;
- struct timer **newheap = xmalloc_array(struct timer *, new_limit + 1);
+ unsigned int old_limit = heap_metadata(heap)->limit;
+ unsigned int new_limit = ((old_limit + 1) << 4) - 1;
+ struct timer **newheap = NULL;
+
+ /* Don't grow the heap beyond what is representable in its metadata. */
+ if ( new_limit == (typeof(heap_metadata(heap)->limit))new_limit &&
+ new_limit + 1 )
+ newheap = xmalloc_array(struct timer *, new_limit + 1);
+ else
+ printk_once(XENLOG_WARNING "CPU%u: timer heap limit reached\n",
+ smp_processor_id());
if ( newheap != NULL )
{
spin_lock_irq(&ts->lock);
@@ -544,7 +549,7 @@ static void dump_timerq(unsigned char ke
struct timers *ts;
unsigned long flags;
s_time_t now = NOW();
- int i, j;
+ unsigned int i, j;
printk("Dumping timer queues:\n");
@@ -556,7 +561,7 @@ static void dump_timerq(unsigned char ke
spin_lock_irqsave(&ts->lock, flags);
for ( j = 1; j <= heap_metadata(ts->heap)->size; j++ )
dump_timer(ts->heap[j], now);
- for ( t = ts->list, j = 0; t != NULL; t = t->list_next, j++ )
+ for ( t = ts->list; t != NULL; t = t->list_next )
dump_timer(t, now);
spin_unlock_irqrestore(&ts->lock, flags);
}
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