[PATCH v12 2/4] lib/intel_device_info: make device info cache thread-safe

[Xin Wang <x.wang@intel.com>]

Replace the per-thread single-entry cache in intel_get_device_info() with a
process-wide cache keyed by devid.

Use igt_map + pthread mutex to store a copy of struct intel_device_info per
device id, and initialize/teardown the cache via igt_constructor/igt_destructor.

Also link igt_map.c into libigt_chipset to provide the map implementation.

Signed-off-by: Xin Wang <x.wang@intel.com>
---
 lib/intel_device_info.c | 91 +++++++++++++++++++++++++++++++++++++----
 lib/meson.build         |  1 +
 2 files changed, 83 insertions(+), 9 deletions(-)

diff --git a/lib/intel_device_info.c b/lib/intel_device_info.c
index 89fa6788f..e97a8caa0 100644
--- a/lib/intel_device_info.c
+++ b/lib/intel_device_info.c
@@ -1,7 +1,10 @@
 #include "intel_chipset.h"
 #include "pciids.h"
 #include "i915_pciids_local.h"
+#include "igt_core.h"
+#include "igt_map.h"
 
+#include <pthread.h>
 #include <strings.h> /* ffs() */
 
 static const struct intel_device_info intel_generic_info = {
@@ -688,6 +691,53 @@ static const struct pci_id_match intel_device_match[] = {
 
 #undef INTEL_PCI_ID_INIT
 
+static struct intel_device_cache {
+	pthread_mutex_t cache_mutex;
+	struct igt_map *map;
+} dev;
+
+static void intel_device_info_cache_init(void)
+{
+	pthread_mutex_init(&dev.cache_mutex, NULL);
+	dev.map = igt_map_create(igt_map_hash_32, igt_map_equal_32);
+}
+
+static void free_device_info(struct igt_map_entry *entry)
+{
+	free(entry->data);
+	free((void *)entry->key);
+}
+
+static void intel_device_info_cache_fini(void)
+{
+	pthread_mutex_lock(&dev.cache_mutex);
+	igt_map_destroy(dev.map, free_device_info);
+	pthread_mutex_unlock(&dev.cache_mutex);
+	pthread_mutex_destroy(&dev.cache_mutex);
+}
+
+static struct intel_device_info *intel_device_info_cache_get(uint16_t devid)
+{
+	struct intel_device_info *info;
+	uint32_t key = devid;
+
+	pthread_mutex_lock(&dev.cache_mutex);
+	info = igt_map_search(dev.map, &key);
+	pthread_mutex_unlock(&dev.cache_mutex);
+
+	return info;
+}
+
+igt_constructor
+{
+	intel_device_info_cache_init();
+}
+
+igt_destructor
+{
+	intel_device_info_cache_fini();
+}
+
 /**
  * intel_get_device_info:
  * @devid: pci device id
@@ -699,24 +749,47 @@ static const struct pci_id_match intel_device_match[] = {
  */
 const struct intel_device_info *intel_get_device_info(uint16_t devid)
 {
-	static __thread const struct intel_device_info *cache = &intel_generic_info;
-	static __thread uint16_t cached_devid;
+	struct intel_device_info *info;
+	struct intel_device_info *new_info = NULL;
+	uint32_t *new_key = NULL;
+	uint32_t key_val = devid;
 	int i;
 
-	if (cached_devid == devid)
-		goto out;
+	info = intel_device_info_cache_get(devid);
+	if (info)
+		return info;
 
-	/* XXX Presort table and bsearch! */
 	for (i = 0; intel_device_match[i].device_id != PCI_MATCH_ANY; i++) {
 		if (devid == intel_device_match[i].device_id)
 			break;
 	}
 
-	cached_devid = devid;
-	cache = (void *)intel_device_match[i].match_data;
+	new_key = malloc(sizeof(*new_key));
+	new_info = malloc(sizeof(*new_info));
+	if (!new_key || !new_info) {
+		free(new_key);
+		free(new_info);
+		return &intel_generic_info;
+	}
+
+	*new_key = devid;
+	memcpy(new_info, (const void *)intel_device_match[i].match_data, sizeof(*new_info));
+
+	/* Another thread may have inserted while we were allocating. */
+	pthread_mutex_lock(&dev.cache_mutex);
+	info = igt_map_search(dev.map, &key_val);
+	if (!info) {
+		igt_map_insert(dev.map, new_key, new_info);
+		info = new_info;
+		new_key = NULL;
+		new_info = NULL;
+	}
+	pthread_mutex_unlock(&dev.cache_mutex);
+
+	free(new_info);
+	free(new_key);
 
-out:
-	return cache;
+	return info;
 }
 
 /**
diff --git a/lib/meson.build b/lib/meson.build
index 1a569ba52..d41540799 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -317,6 +317,7 @@ igt_deps = [ lib_igt ] + lib_deps
 lin_igt_chipset_build = static_library('igt_chipset',
                                        ['intel_chipset.c',
 					'intel_device_info.c',
+					'igt_map.c',
 					'intel_cmds_info.c'],
                                        include_directories : inc)
 
-- 
2.43.0