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Route attribute usecount doesn't need to synchronize on unlock

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This commit is contained in:
Maria Matejka 2024-06-20 20:37:21 +02:00
parent 2c4b368176
commit 4998ca5554
1 changed files with 19 additions and 10 deletions
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29
nest/rt-attr.c
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@ -1733,8 +1733,8 @@ ea_lookup_slow(ea_list *o, u32 squash_upto, enum ea_stored oid)
return r->l;
}
#define EA_UC_SUB (1ULL << 56)
#define EA_UC_IN_PROGRESS(x) ((x) >> 56)
#define EA_UC_SUB (1ULL << 44)
#define EA_UC_IN_PROGRESS(x) ((x) >> 44)
#define EA_UC_ASSIGNED(x) ((x) & (EA_UC_SUB-1))
#define EA_UC_DONE(x) (EA_UC_ASSIGNED(x) == EA_UC_IN_PROGRESS(x))
@ -1744,11 +1744,8 @@ ea_free_deferred(struct deferred_call *dc)
{
struct ea_storage *r = ea_get_storage(SKIP_BACK(struct ea_free_deferred, dc, dc)->attrs);
/* Wait until the previous free has ended */
u64 prev;
do prev = atomic_fetch_or_explicit(&r->uc, EA_UC_SUB, memory_order_acq_rel);
while (prev & EA_UC_SUB);
/* Indicate free intent */
u64 prev = atomic_fetch_add_explicit(&r->uc, EA_UC_SUB, memory_order_acq_rel);
prev |= EA_UC_SUB;
if (!EA_UC_DONE(prev))
@ -1759,6 +1756,18 @@ ea_free_deferred(struct deferred_call *dc)
return;
}
/* Wait for others to finish */
while (EA_UC_DONE(prev) && (EA_UC_IN_PROGRESS(prev) > 1))
prev = atomic_load_explicit(&r->uc, memory_order_acquire);
if (!EA_UC_DONE(prev))
{
/* Somebody else has found us inbetween, no need to free */
ASSERT_DIE(EA_UC_IN_PROGRESS(prev) < EA_UC_ASSIGNED(prev));
atomic_fetch_sub_explicit(&r->uc, EA_UC_SUB + 1, memory_order_acq_rel);
return;
}
/* We are the last one to free this ea */
RTA_LOCK;
@ -1767,16 +1776,16 @@ ea_free_deferred(struct deferred_call *dc)
/* Somebody has cloned this rta inbetween. This sometimes happens. */
prev = atomic_load_explicit(&r->uc, memory_order_acquire);
if (!EA_UC_DONE(prev))
if (!EA_UC_DONE(prev) || (EA_UC_IN_PROGRESS(prev) > 1))
{
/* Reinsert the ea */
/* Reinsert the ea and go away */
SPINHASH_INSERT(rta_hash_table, RTAH, r);
atomic_fetch_sub_explicit(&r->uc, EA_UC_SUB + 1, memory_order_acq_rel);
RTA_UNLOCK;
return;
}
/* Fine, wait until everybody is actually done */
/* Fine, now everybody is actually done */
ASSERT_DIE(atomic_load_explicit(&r->uc, memory_order_acquire) == EA_UC_SUB + 1);
/* And now we can free the object, finally */