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fix race conditions in instance id-to-key lookup

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this is just an intermediate step: firstly, iid-to-key lookup is a linear scan; secondly, the lookup should happen on the RHC or the WHC and not on some internal map to associates key values with instance handles and is independent of entities

Signed-off-by: Erik Boasson <eb@ilities.com>
This commit is contained in:
Erik Boasson 2018-12-19 13:29:53 +01:00
parent 0f7ce1ac43
commit 179a35d192
3 changed files with 45 additions and 74 deletions
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1
src/core/ddsi/include/ddsi/ddsi_tkmap.h
View file

@ -36,7 +36,6 @@ struct ddsi_tkmap * ddsi_tkmap_new (void);
void ddsi_tkmap_free (_Inout_ _Post_invalid_ struct ddsi_tkmap *tkmap);
void ddsi_tkmap_instance_ref (_In_ struct ddsi_tkmap_instance *tk);
uint64_t ddsi_tkmap_lookup (_In_ struct ddsi_tkmap *tkmap, _In_ const struct ddsi_serdata *serdata);
_Check_return_ bool ddsi_tkmap_get_key (_In_ struct ddsi_tkmap * map, const struct ddsi_sertopic *topic, _In_ uint64_t iid, _Out_ void * sample);
_Check_return_ struct ddsi_tkmap_instance * ddsi_tkmap_find(
_In_ struct ddsi_serdata * sd,
_In_ const bool rd,

74
src/core/ddsi/src/ddsi_tkmap.c
View file

@ -82,7 +82,7 @@ static int dds_tk_equals_void (const void *a, const void *b)
return dds_tk_equals (a, b);
}
struct ddsi_tkmap * ddsi_tkmap_new (void)
struct ddsi_tkmap *ddsi_tkmap_new (void)
{
struct ddsi_tkmap *tkmap = dds_alloc (sizeof (*tkmap));
tkmap->m_hh = ut_chhNew (1, dds_tk_hash_void, dds_tk_equals_void, gc_buckets);
@ -111,64 +111,32 @@ uint64_t ddsi_tkmap_lookup (_In_ struct ddsi_tkmap * map, _In_ const struct ddsi
{
struct ddsi_tkmap_instance dummy;
struct ddsi_tkmap_instance * tk;
assert (vtime_awake_p(lookup_thread_state()->vtime));
dummy.m_sample = (struct ddsi_serdata *) sd;
tk = ut_chhLookup (map->m_hh, &dummy);
return (tk) ? tk->m_iid : DDS_HANDLE_NIL;
}
typedef struct
{
const struct ddsi_sertopic *topic;
uint64_t m_iid;
void * m_sample;
bool m_ret;
}
tkmap_get_key_arg;
static void dds_tkmap_get_key_fn (void * vtk, void * varg)
{
struct ddsi_tkmap_instance * tk = vtk;
tkmap_get_key_arg * arg = (tkmap_get_key_arg*) varg;
if (tk->m_iid == arg->m_iid)
{
ddsi_serdata_topicless_to_sample (arg->topic, tk->m_sample, arg->m_sample, 0, 0);
arg->m_ret = true;
}
}
_Check_return_
bool ddsi_tkmap_get_key (_In_ struct ddsi_tkmap * map, const struct ddsi_sertopic *topic, _In_ uint64_t iid, _Out_ void * sample)
struct ddsi_tkmap_instance *ddsi_tkmap_find_by_id (_In_ struct ddsi_tkmap *map, _In_ uint64_t iid)
{
tkmap_get_key_arg arg = { topic, iid, sample, false };
os_mutexLock (&map->m_lock);
ut_chhEnumUnsafe (map->m_hh, dds_tkmap_get_key_fn, &arg);
os_mutexUnlock (&map->m_lock);
return arg.m_ret;
}
typedef struct
{
uint64_t m_iid;
struct ddsi_tkmap_instance * m_inst;
}
tkmap_get_inst_arg;
static void dds_tkmap_get_inst_fn (void * vtk, void * varg)
{
struct ddsi_tkmap_instance * tk = vtk;
tkmap_get_inst_arg * arg = (tkmap_get_inst_arg*) varg;
if (tk->m_iid == arg->m_iid)
{
arg->m_inst = tk;
}
}
_Check_return_
struct ddsi_tkmap_instance * ddsi_tkmap_find_by_id (_In_ struct ddsi_tkmap * map, _In_ uint64_t iid)
{
tkmap_get_inst_arg arg = { iid, NULL };
ut_chhEnumUnsafe (map->m_hh, dds_tkmap_get_inst_fn, &arg);
return arg.m_inst;
/* This is not a function that should be used liberally, as it linearly scans the key-to-iid map. */
struct ut_chhIter it;
struct ddsi_tkmap_instance *tk;
uint32_t refc;
assert (vtime_awake_p(lookup_thread_state()->vtime));
for (tk = ut_chhIterFirst (map->m_hh, &it); tk; tk = ut_chhIterNext (&it))
if (tk->m_iid == iid)
break;
if (tk == NULL)
/* Common case of it not existing at all */
return NULL;
else if (!((refc = os_atomic_ld32 (&tk->m_refc)) & REFC_DELETE) && os_atomic_cas32 (&tk->m_refc, refc, refc+1))
/* Common case of it existing, not in the process of being deleted and no one else concurrently modifying the refcount */
return tk;
else
/* Let key value lookup handle the possible CAS loop and the complicated cases */
return ddsi_tkmap_find (tk->m_sample, false, false);
}
/* Debug keyhash generation for debug and coverage builds */
@ -193,6 +161,7 @@ struct ddsi_tkmap_instance * ddsi_tkmap_find(
struct ddsi_tkmap_instance * tk;
struct ddsi_tkmap * map = gv.m_tkmap;
assert (vtime_awake_p(lookup_thread_state()->vtime));
dummy.m_sample = sd;
retry:
if ((tk = ut_chhLookup(map->m_hh, &dummy)) != NULL)
@ -242,7 +211,6 @@ retry:
_Check_return_
struct ddsi_tkmap_instance * ddsi_tkmap_lookup_instance_ref (_In_ struct ddsi_serdata * sd)
{
assert (vtime_awake_p (lookup_thread_state ()->vtime));
return ddsi_tkmap_find (sd, true, true);
}