diff options
author | Emilio G. Cota <cota@braap.org> | 2016-07-22 12:36:30 -0400 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-08-02 12:03:58 +0200 |
commit | 7266ae91a111001abda65c79299c9b7e365456b6 (patch) | |
tree | 9bbd8547070f5f5429a081f539ea85ddb5dcb38b /util/qht.c | |
parent | 767db021bc45affa7a7c20ea21730d2867a0c37f (diff) |
qht: do not segfault when gathering stats from an uninitialized qht
So far, QHT functions assume that the passed qht has previously been
initialized--otherwise they segfault.
This patch makes an exception for qht_statistics_init, with the goal
of simplifying calling code. For instance, qht_statistics_init is
called from the 'info jit' dump, and given that under KVM the TB qht
is never initialized, we get a segfault. Thus, instead of complicating
the 'info jit' code with additional checks, let's allow passing an
uninitialized qht to qht_statistics_init.
While at it, add a test for this to test-qht.
Before the patch (for $ qemu -enable-kvm [...]):
(qemu) info jit
[...]
direct jump count 0 (0%) (2 jumps=0 0%)
Program received signal SIGSEGV, Segmentation fault.
After the patch the "TB hash buckets", "TB hash occupancy"
and "TB hash avg chain" lines are omitted.
(qemu) info jit
[...]
direct jump count 0 (0%) (2 jumps=0 0%)
TB hash buckets 0/0 (-nan% head buckets used)
TB hash occupancy nan% avg chain occ. Histogram: (null)
TB hash avg chain nan buckets. Histogram: (null)
[...]
Reported by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1469205390-14369-1-git-send-email-cota@braap.org>
[Extract printing statistics to an entirely separate function. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'util/qht.c')
-rw-r--r-- | util/qht.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/util/qht.c b/util/qht.c index 28ce289245..16a8d7950e 100644 --- a/util/qht.c +++ b/util/qht.c @@ -789,11 +789,16 @@ void qht_statistics_init(struct qht *ht, struct qht_stats *stats) map = atomic_rcu_read(&ht->map); - stats->head_buckets = map->n_buckets; stats->used_head_buckets = 0; stats->entries = 0; qdist_init(&stats->chain); qdist_init(&stats->occupancy); + /* bail out if the qht has not yet been initialized */ + if (unlikely(map == NULL)) { + stats->head_buckets = 0; + return; + } + stats->head_buckets = map->n_buckets; for (i = 0; i < map->n_buckets; i++) { struct qht_bucket *head = &map->buckets[i]; |