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[Qemu-devel] [PULL 08/25] qht: do not segfault when gathering stats from
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 08/25] qht: do not segfault when gathering stats from an uninitialized qht |
Date: |
Tue, 2 Aug 2016 21:39:18 +0200 |
From: "Emilio G. Cota" <address@hidden>
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 <address@hidden>
Signed-off-by: Emilio G. Cota <address@hidden>
Message-Id: <address@hidden>
[Extract printing statistics to an entirely separate function. - Paolo]
Signed-off-by: Paolo Bonzini <address@hidden>
---
tests/test-qht.c | 4 ++++
translate-all.c | 70 +++++++++++++++++++++++++++++++-------------------------
util/qht.c | 7 +++++-
3 files changed, 49 insertions(+), 32 deletions(-)
diff --git a/tests/test-qht.c b/tests/test-qht.c
index f1d6283..46a64b6 100644
--- a/tests/test-qht.c
+++ b/tests/test-qht.c
@@ -95,8 +95,12 @@ static void iter_check(unsigned int count)
static void qht_do_test(unsigned int mode, size_t init_entries)
{
+ /* under KVM we might fetch stats from an uninitialized qht */
+ check_n(0);
+
qht_init(&ht, 0, mode);
+ check_n(0);
insert(0, N);
check(0, N, true);
check_n(N);
diff --git a/translate-all.c b/translate-all.c
index 0d47c1c..efeba29 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -1663,15 +1663,50 @@ void tb_flush_jmp_cache(CPUState *cpu, target_ulong
addr)
TB_JMP_PAGE_SIZE * sizeof(TranslationBlock *));
}
+static void print_qht_statistics(FILE *f, fprintf_function cpu_fprintf,
+ struct qht_stats hst)
+{
+ uint32_t hgram_opts;
+ size_t hgram_bins;
+ char *hgram;
+
+ if (!hst.head_buckets) {
+ return;
+ }
+ cpu_fprintf(f, "TB hash buckets %zu/%zu (%0.2f%% head buckets used)\n",
+ hst.used_head_buckets, hst.head_buckets,
+ (double)hst.used_head_buckets / hst.head_buckets * 100);
+
+ hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
+ hgram_opts |= QDIST_PR_100X | QDIST_PR_PERCENT;
+ if (qdist_xmax(&hst.occupancy) - qdist_xmin(&hst.occupancy) == 1) {
+ hgram_opts |= QDIST_PR_NODECIMAL;
+ }
+ hgram = qdist_pr(&hst.occupancy, 10, hgram_opts);
+ cpu_fprintf(f, "TB hash occupancy %0.2f%% avg chain occ. Histogram:
%s\n",
+ qdist_avg(&hst.occupancy) * 100, hgram);
+ g_free(hgram);
+
+ hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
+ hgram_bins = qdist_xmax(&hst.chain) - qdist_xmin(&hst.chain);
+ if (hgram_bins > 10) {
+ hgram_bins = 10;
+ } else {
+ hgram_bins = 0;
+ hgram_opts |= QDIST_PR_NODECIMAL | QDIST_PR_NOBINRANGE;
+ }
+ hgram = qdist_pr(&hst.chain, hgram_bins, hgram_opts);
+ cpu_fprintf(f, "TB hash avg chain %0.3f buckets. Histogram: %s\n",
+ qdist_avg(&hst.chain), hgram);
+ g_free(hgram);
+}
+
void dump_exec_info(FILE *f, fprintf_function cpu_fprintf)
{
int i, target_code_size, max_target_code_size;
int direct_jmp_count, direct_jmp2_count, cross_page;
TranslationBlock *tb;
struct qht_stats hst;
- uint32_t hgram_opts;
- size_t hgram_bins;
- char *hgram;
target_code_size = 0;
max_target_code_size = 0;
@@ -1724,34 +1759,7 @@ void dump_exec_info(FILE *f, fprintf_function
cpu_fprintf)
tcg_ctx.tb_ctx.nb_tbs : 0);
qht_statistics_init(&tcg_ctx.tb_ctx.htable, &hst);
-
- cpu_fprintf(f, "TB hash buckets %zu/%zu (%0.2f%% head buckets used)\n",
- hst.used_head_buckets, hst.head_buckets,
- (double)hst.used_head_buckets / hst.head_buckets * 100);
-
- hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
- hgram_opts |= QDIST_PR_100X | QDIST_PR_PERCENT;
- if (qdist_xmax(&hst.occupancy) - qdist_xmin(&hst.occupancy) == 1) {
- hgram_opts |= QDIST_PR_NODECIMAL;
- }
- hgram = qdist_pr(&hst.occupancy, 10, hgram_opts);
- cpu_fprintf(f, "TB hash occupancy %0.2f%% avg chain occ. Histogram:
%s\n",
- qdist_avg(&hst.occupancy) * 100, hgram);
- g_free(hgram);
-
- hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
- hgram_bins = qdist_xmax(&hst.chain) - qdist_xmin(&hst.chain);
- if (hgram_bins > 10) {
- hgram_bins = 10;
- } else {
- hgram_bins = 0;
- hgram_opts |= QDIST_PR_NODECIMAL | QDIST_PR_NOBINRANGE;
- }
- hgram = qdist_pr(&hst.chain, hgram_bins, hgram_opts);
- cpu_fprintf(f, "TB hash avg chain %0.3f buckets. Histogram: %s\n",
- qdist_avg(&hst.chain), hgram);
- g_free(hgram);
-
+ print_qht_statistics(f, cpu_fprintf, hst);
qht_statistics_destroy(&hst);
cpu_fprintf(f, "\nStatistics:\n");
diff --git a/util/qht.c b/util/qht.c
index 28ce289..16a8d79 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];
--
2.7.4
- [Qemu-devel] [PULL 00/25] Misc QEMU fixes for 2016-08-02, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 01/25] util/qht: Document memory ordering assumptions, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 02/25] numa: set the memory backend "is_mapped" field, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 03/25] fix qemu exit on memory hotplug when allocation fails at prealloc time, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 04/25] checkpatch: add check for bzero, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 06/25] util: drop unix_nonblocking_connect(), Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 05/25] util: drop inet_nonblocking_connect(), Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 08/25] qht: do not segfault when gathering stats from an uninitialized qht,
Paolo Bonzini <=
- [Qemu-devel] [PULL 09/25] target-i386: fix typo in xsetbv implementation, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 10/25] qdist: fix memory leak during binning, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 07/25] util: Drop inet_listen(), Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 11/25] qdist: use g_realloc_n instead of g_realloc, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 12/25] qdist: return "(empty)" instead of NULL when printing an empty dist, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 13/25] mptsas: really fix migration compatibility, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 14/25] i2c: fix migration regression introduced by broadcast support, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 15/25] nbd: Fix bad flag detection on server, Paolo Bonzini, 2016/08/02
- [Qemu-devel] [PULL 19/25] fw_cfg: Make base type "fw_cfg" abstract, Paolo Bonzini, 2016/08/02