The patch titled
timer statistics: fix race
has been removed from the -mm tree. Its filename was
something-goes-wrong-with-timer-statistics.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: timer statistics: fix race
From: Bjorn Steinbrink <B.Steinbrink@xxxxxx>
Fix two races in the timer stats lookup code. One by ensuring that the
initialization of a new entry is finished upon insertion of that entry.
The other by cleaning up the hash table when the entries array is cleared,
so that we don't have any "pre-inserted" entries.
Thanks to Eric Dumazet for reminding me of the memory barriers.
Signed-off-by: Bjorn Steinbrink <B.Steinbrink@xxxxxx>
Signed-off-by: Ian Kumlien <pomac@xxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/time/timer_stats.c | 37 ++++++++++++++++++++----------------
1 file changed, 21 insertions(+), 16 deletions(-)
diff -puN kernel/time/timer_stats.c~something-goes-wrong-with-timer-statistics kernel/time/timer_stats.c
--- a/kernel/time/timer_stats.c~something-goes-wrong-with-timer-statistics
+++ a/kernel/time/timer_stats.c
@@ -117,21 +117,6 @@ static struct entry entries[MAX_ENTRIES]
static atomic_t overflow_count;
-static void reset_entries(void)
-{
- nr_entries = 0;
- memset(entries, 0, sizeof(entries));
- atomic_set(&overflow_count, 0);
-}
-
-static struct entry *alloc_entry(void)
-{
- if (nr_entries >= MAX_ENTRIES)
- return NULL;
-
- return entries + nr_entries++;
-}
-
/*
* The entries are in a hash-table, for fast lookup:
*/
@@ -149,6 +134,22 @@ static struct entry *alloc_entry(void)
static struct entry *tstat_hash_table[TSTAT_HASH_SIZE] __read_mostly;
+static void reset_entries(void)
+{
+ nr_entries = 0;
+ memset(entries, 0, sizeof(entries));
+ memset(tstat_hash_table, 0, sizeof(tstat_hash_table));
+ atomic_set(&overflow_count, 0);
+}
+
+static struct entry *alloc_entry(void)
+{
+ if (nr_entries >= MAX_ENTRIES)
+ return NULL;
+
+ return entries + nr_entries++;
+}
+
static int match_entries(struct entry *entry1, struct entry *entry2)
{
return entry1->timer == entry2->timer &&
@@ -202,12 +203,15 @@ static struct entry *tstat_lookup(struct
if (curr) {
*curr = *entry;
curr->count = 0;
+ curr->next = NULL;
memcpy(curr->comm, comm, TASK_COMM_LEN);
+
+ smp_mb(); /* Ensure that curr is initialized before insert */
+
if (prev)
prev->next = curr;
else
*head = curr;
- curr->next = NULL;
}
out_unlock:
spin_unlock(&table_lock);
@@ -360,6 +364,7 @@ static ssize_t tstats_write(struct file
if (!active) {
reset_entries();
time_start = ktime_get();
+ smp_mb();
active = 1;
}
break;
_
Patches currently in -mm which might be from B.Steinbrink@xxxxxx are
origin.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
