diff options
author | Bjorn Steinbrink <B.Steinbrink@gmx.de> | 2007-06-01 07:47:15 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-06-01 15:18:30 (GMT) |
commit | 9fcc15ec3c1c287a781a4620e52522b6186f26f6 (patch) | |
tree | 86a0214fc404c0ca6e0ca283c83f22bd15aa2eb4 /kernel/time | |
parent | c79d9c9e9ace5eeae54f484f62fbd86bf27a344a (diff) | |
download | linux-9fcc15ec3c1c287a781a4620e52522b6186f26f6.tar.xz |
timer statistics: fix race
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@gmx.de>
Signed-off-by: Ian Kumlien <pomac@vapor.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time')
-rw-r--r-- | kernel/time/timer_stats.c | 37 |
1 files changed, 21 insertions, 16 deletions
diff --git a/kernel/time/timer_stats.c b/kernel/time/timer_stats.c index 868f1bc..fa3d380 100644 --- a/kernel/time/timer_stats.c +++ b/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 entry *entry, char *comm) 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 *file, const char __user *buf, if (!active) { reset_entries(); time_start = ktime_get(); + smp_mb(); active = 1; } break; |