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Jul 10, 2025
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repair: fix forest and fec chainer publish edge cases #5519

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2 changes: 1 addition & 1 deletion src/app/firedancer/config/default.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -1148,7 +1148,7 @@ user = ""
# startup, when the validator is catching up from the snapshot
# slot, but still maintaining and receiving new turbine slots.
# Must be power of 2
slot_max = 1024
slot_max = 4096

[tiles.replay]
cluster_version = "1.18.0"
Expand Down
187 changes: 100 additions & 87 deletions src/discof/forest/fd_forest.c
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Expand Up @@ -38,19 +38,21 @@ fd_forest_new( void * shmem, ulong ele_max, ulong seed ) {
FD_SCRATCH_ALLOC_INIT( l, shmem );
forest = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_align(), sizeof(fd_forest_t) );
void * ver = FD_SCRATCH_ALLOC_APPEND( l, fd_fseq_align(), fd_fseq_footprint() );
void * pool = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_pool_align(), fd_forest_pool_footprint( ele_max ) );
void * pool = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_pool_align(), fd_forest_pool_footprint ( ele_max ) );
void * ancestry = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_ancestry_align(), fd_forest_ancestry_footprint( ele_max ) );
void * frontier = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_frontier_align(), fd_forest_frontier_footprint( ele_max ) );
void * orphaned = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_orphaned_align(), fd_forest_orphaned_footprint( ele_max ) );
void * deque = FD_SCRATCH_ALLOC_APPEND( l, fd_forest_deque_align(), fd_forest_deque_footprint ( ele_max ) );
FD_TEST( FD_SCRATCH_ALLOC_FINI( l, fd_forest_align() ) == (ulong)shmem + footprint );

forest->root = ULONG_MAX;
forest->wksp_gaddr = fd_wksp_gaddr_fast( wksp, forest );
forest->ver_gaddr = fd_wksp_gaddr_fast( wksp, fd_fseq_join ( fd_fseq_new ( ver, FD_FOREST_VER_UNINIT ) ) );
forest->pool_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_pool_join ( fd_forest_pool_new ( pool, ele_max ) ) );
forest->ancestry_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_ancestry_join( fd_forest_ancestry_new( ancestry, ele_max, seed ) ) );
forest->frontier_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_frontier_join( fd_forest_frontier_new( frontier, ele_max, seed ) ) );
forest->orphaned_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_orphaned_join( fd_forest_orphaned_new( orphaned, ele_max, seed ) ) );
forest->ver_gaddr = fd_wksp_gaddr_fast( wksp, fd_fseq_join ( fd_fseq_new ( ver, FD_FOREST_VER_UNINIT ) ) );
forest->pool_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_pool_join ( fd_forest_pool_new ( pool, ele_max ) ) );
forest->ancestry_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_ancestry_join( fd_forest_ancestry_new( ancestry, ele_max, seed ) ) );
forest->frontier_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_frontier_join( fd_forest_frontier_new( frontier, ele_max, seed ) ) );
forest->orphaned_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_orphaned_join( fd_forest_orphaned_new( orphaned, ele_max, seed ) ) );
forest->deque_gaddr = fd_wksp_gaddr_fast( wksp, fd_forest_deque_join ( fd_forest_deque_new ( deque, ele_max ) ) );

FD_COMPILER_MFENCE();
FD_VOLATILE( forest->magic ) = FD_FOREST_MAGIC;
Expand Down Expand Up @@ -126,7 +128,6 @@ fd_forest_init( fd_forest_t * forest, ulong root_slot ) {

fd_forest_ele_t * root_ele = fd_forest_pool_ele_acquire( pool );
root_ele->slot = root_slot;
root_ele->prev = null;
root_ele->parent = null;
root_ele->child = null;
root_ele->sibling = null;
Expand Down Expand Up @@ -188,16 +189,9 @@ fd_forest_verify( fd_forest_t const * forest ) {
return 0;
}

/* query queries for a connected ele keyed by slot. does not return
orphaned ele. */

static fd_forest_ele_t *
ancestry_frontier_query( fd_forest_t * forest, ulong slot ) {
fd_forest_ele_t * pool = fd_forest_pool( forest );
fd_forest_ele_t * ele = NULL;
ele = fd_forest_ancestry_ele_query( fd_forest_ancestry( forest ), &slot, NULL, pool );
ele = fd_ptr_if( !ele, fd_forest_frontier_ele_query( fd_forest_frontier( forest ), &slot, NULL, pool ), ele );
return ele;
FD_FN_PURE static inline ulong *
fd_forest_deque( fd_forest_t * forest ) {
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should this be in the .h?

return fd_wksp_laddr_fast( fd_forest_wksp( forest ), forest->deque_gaddr );
}

/* remove removes and returns a connected ele from ancestry or frontier
Expand Down Expand Up @@ -233,41 +227,6 @@ link( fd_forest_t * forest, fd_forest_ele_t * parent, fd_forest_ele_t * child )
child->parent = fd_forest_pool_idx( pool, parent );
}

/* link_orphans performs a BFS beginning from head using BFS. head is
the first element of a linked list representing the BFS queue. If the
starting orphan is connected to the ancestry tree (ie. its parent is
in the map), it is linked to the tree and removed from the orphaned
map, and any of its orphaned children are added to the queue (linking
a parent also links its direct children). Otherwise it remains in the
orphaned map. The BFS continues until the queue is empty. */

FD_FN_UNUSED static void
link_orphans( fd_forest_t * forest, fd_forest_ele_t * head ) {
fd_forest_ele_t * pool = fd_forest_pool( forest );
ulong null = fd_forest_pool_idx_null( pool );
fd_forest_ancestry_t * ancestry = fd_forest_ancestry( forest );
fd_forest_orphaned_t * orphaned = fd_forest_orphaned( forest );
fd_forest_ele_t * tail = head;
fd_forest_ele_t * prev = NULL;
while( FD_LIKELY( head ) ) { /* while queue is non-empty */
if( FD_LIKELY( fd_forest_orphaned_ele_remove( orphaned, &head->slot, NULL, pool ) ) ) { /* head is orphan root */
fd_forest_ancestry_ele_insert( ancestry, head, pool );
fd_forest_ele_t * child = fd_forest_pool_ele( pool, head->child );
while( FD_LIKELY( child ) ) { /* append children to frontier */
tail->prev = fd_forest_pool_idx( pool, child ); /* safe to overwrite prev */
tail = fd_forest_pool_ele( pool, tail->prev );
tail->prev = null;
ulong sibling = child->sibling;
child->sibling = null;
child = fd_forest_pool_ele( pool, sibling );
}
}
prev = head;
head = fd_forest_pool_ele( pool, head->prev );
prev->prev = null;
}
}

/* advance_frontier attempts to advance the frontier beginning from slot
using BFS. head is the first element of a linked list representing
the BFS queue. A slot can be advanced if all shreds for the block
Expand All @@ -276,36 +235,36 @@ link_orphans( fd_forest_t * forest, fd_forest_ele_t * head ) {
static void
advance_frontier( fd_forest_t * forest, ulong slot, ushort parent_off ) {
fd_forest_ele_t * pool = fd_forest_pool( forest );
ulong null = fd_forest_pool_idx_null( pool );
fd_forest_ancestry_t * ancestry = fd_forest_ancestry( forest );
fd_forest_frontier_t * frontier = fd_forest_frontier( forest );
ulong * queue = fd_forest_deque( forest );

fd_forest_ele_t * ele;
ele = fd_forest_frontier_ele_query( fd_forest_frontier( forest ), &slot, NULL, pool );
ulong parent_slot = slot - parent_off;
ele = fd_ptr_if( !ele, fd_forest_frontier_ele_query( fd_forest_frontier( forest ), &parent_slot, NULL, pool ), ele );
if( FD_UNLIKELY( !ele ) ) return;

fd_forest_ele_t * head = ele;
fd_forest_ele_t * tail = head;
fd_forest_ele_t * prev = NULL;
# if FD_FOREST_USE_HANDHOLDING
FD_TEST( fd_forest_deque_cnt( queue ) == 0 );
# endif

while( FD_LIKELY( head ) ) {
/* BFS elements as pool idxs */
fd_forest_deque_push_tail( queue, fd_forest_pool_idx( pool, ele ) );
while( FD_LIKELY( fd_forest_deque_cnt( queue ) ) ) {
fd_forest_ele_t * head = fd_forest_pool_ele( pool, fd_forest_deque_pop_head( queue ) );
fd_forest_ele_t * child = fd_forest_pool_ele( pool, head->child );
if( FD_LIKELY( child && head->complete_idx != UINT_MAX && head->buffered_idx == head->complete_idx ) ) {
fd_forest_frontier_ele_remove( frontier, &head->slot, NULL, pool );
fd_forest_ancestry_ele_insert( ancestry, head, pool );
while( FD_LIKELY( child ) ) { /* append children to frontier */
fd_forest_ancestry_ele_remove( ancestry, &child->slot, NULL, pool );
fd_forest_frontier_ele_insert( frontier, child, pool );
tail->prev = fd_forest_pool_idx( pool, child );
tail = fd_forest_pool_ele( pool, tail->prev );
tail->prev = fd_forest_pool_idx_null( pool );
child = fd_forest_pool_ele( pool, child->sibling );

fd_forest_deque_push_tail( queue, fd_forest_pool_idx( pool, child ) );
child = fd_forest_pool_ele( pool, child->sibling );
}
}
prev = head;
head = fd_forest_pool_ele( pool, head->prev );
prev->prev = null;
}
}

Expand All @@ -330,7 +289,6 @@ acquire( fd_forest_t * forest, ulong slot ) {
ulong null = fd_forest_pool_idx_null( pool );

ele->slot = slot;
ele->prev = null;
ele->next = null;
ele->parent = null;
ele->child = null;
Expand Down Expand Up @@ -382,9 +340,6 @@ insert( fd_forest_t * forest, ulong slot, ushort parent_off ) {

fd_forest_ele_t *
fd_forest_query( fd_forest_t * forest, ulong slot ) {
# if FD_FOREST_USE_HANDHOLDING
FD_TEST( slot > fd_forest_root_slot( forest ) ); /* caller error - inval */
# endif
return query( forest, slot );
}

Expand Down Expand Up @@ -433,50 +388,108 @@ fd_forest_publish( fd_forest_t * forest, ulong new_root_slot ) {

fd_forest_ancestry_t * ancestry = fd_forest_ancestry( forest );
fd_forest_frontier_t * frontier = fd_forest_frontier( forest );
fd_forest_orphaned_t * orphaned = fd_forest_orphaned( forest );
fd_forest_ele_t * pool = fd_forest_pool( forest );
ulong null = fd_forest_pool_idx_null( pool );
ulong * queue = fd_forest_deque( forest );

fd_forest_ele_t * old_root_ele = fd_forest_pool_ele( pool, forest->root );
fd_forest_ele_t * new_root_ele = ancestry_frontier_query( forest, new_root_slot );
fd_forest_ele_t * new_root_ele = query( forest, new_root_slot );

# if FD_FOREST_USE_HANDHOLDING
FD_TEST( new_root_ele ); /* caller error - not found */
FD_TEST( new_root_ele->slot > old_root_ele->slot ); /* caller error - inval */
if( FD_LIKELY( new_root_ele ) ) {
FD_TEST( new_root_ele->slot > old_root_ele->slot ); /* caller error - inval */
}
# endif

/* Edge case where if we haven't been getting repairs, and we have a
gap between the root and orphans. we publish forward to a slot that
we don't have. This only case this should be happening is when we
load a second incremental and that incremental slot lives in the
gap. In that case this isn't a bug, but we should be treating this
new root like the snapshot slot / init root. Should be happening
very rarely given a well-functioning repair. */

if( FD_UNLIKELY( !new_root_ele ) ) {
new_root_ele = acquire( forest, new_root_slot );
new_root_ele->complete_idx = 0;
new_root_ele->buffered_idx = 0;
fd_forest_frontier_ele_insert( frontier, new_root_ele, pool );
}

/* First, remove the previous root, and add it to a FIFO prune queue.
head points to the queue head (initialized with old_root_ele). */

# if FD_FOREST_USE_HANDHOLDING
FD_TEST( fd_forest_deque_cnt( queue ) == 0 );
# endif
fd_forest_ele_t * head = ancestry_frontier_remove( forest, old_root_ele->slot );
head->next = null;
fd_forest_ele_t * tail = head;
if( FD_LIKELY( head ) ) fd_forest_deque_push_tail( queue, fd_forest_pool_idx( pool, head ) );

/* Second, BFS down the tree, inserting each ele into the prune queue
except for the new root. Loop invariant: head always descends from
old_root_ele and never descends from new_root_ele. */

while( head ) {
while( FD_LIKELY( fd_forest_deque_cnt( queue ) ) ) {
head = fd_forest_pool_ele( pool, fd_forest_deque_pop_head( queue ) );
fd_forest_ele_t * child = fd_forest_pool_ele( pool, head->child );
while( FD_LIKELY( child ) ) {
if( FD_LIKELY( child != new_root_ele ) ) { /* do not prune new root or descendants */
ulong idx = fd_forest_ancestry_idx_remove( ancestry, &child->slot, null, pool );
idx = fd_ulong_if( idx != null, idx, fd_forest_frontier_idx_remove( frontier, &child->slot, null, pool ) );
tail->next = idx; /* insert prune queue */
# if FD_FOREST_USE_HANDHOLDING
FD_TEST( tail->next != null ); /* programming error in BFS */
# endif
tail = fd_forest_pool_ele( pool, tail->next ); /* advance prune queue */
tail->next = null;
ulong idx = fd_forest_ancestry_idx_remove( ancestry, &child->slot, null, pool );
idx = fd_ulong_if( idx != null, idx, fd_forest_frontier_idx_remove( frontier, &child->slot, null, pool ) );
fd_forest_deque_push_tail( queue, idx );
}
child = fd_forest_pool_ele( pool, child->sibling );
}
fd_forest_ele_t * next = fd_forest_pool_ele( pool, head->next ); /* FIFO pop */
fd_forest_pool_ele_release( pool, head ); /* free head */
head = next;
fd_forest_pool_ele_release( pool, head );
}

/* If there is nothing on the frontier, we have hit an edge case
during catching up where all of our frontiers were < the new root.
In that case we need to continue repairing from the new root, so
add it to the frontier. */

if( FD_UNLIKELY( fd_forest_frontier_iter_done( fd_forest_frontier_iter_init( frontier, pool ), frontier, pool ) ) ) {
fd_forest_ele_t * remove = fd_forest_ancestry_ele_remove( ancestry, &new_root_ele->slot, NULL, pool );
if( FD_UNLIKELY( !remove ) ) {
/* Very rare case where during second incremental load we could publish to an orphaned slot */
remove = fd_forest_orphaned_ele_remove( orphaned, &new_root_ele->slot, NULL, pool );
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clear remove->next

}
FD_TEST( remove == new_root_ele );
fd_forest_frontier_ele_insert( frontier, new_root_ele, pool );
new_root_ele->complete_idx = 0;
new_root_ele->buffered_idx = 0;
advance_frontier( forest, new_root_ele->slot, 0 );
}

new_root_ele->parent = null; /* unlink new root from parent */
forest->root = fd_forest_ancestry_idx_query( ancestry, &new_root_slot, null, pool );
forest->root = fd_forest_pool_idx( pool, new_root_ele );

/* Lastly, cleanup orphans if there orphan heads < new_root_slot.
First, add any relevant orphans to the prune queue. */

for( fd_forest_orphaned_iter_t iter = fd_forest_orphaned_iter_init( orphaned, pool );
!fd_forest_orphaned_iter_done( iter, orphaned, pool );
iter = fd_forest_orphaned_iter_next( iter, orphaned, pool ) ) {
fd_forest_ele_t * ele = fd_forest_orphaned_iter_ele( iter, orphaned, pool );
if( FD_UNLIKELY( ele->slot < new_root_slot ) ) {
fd_forest_deque_push_tail( queue, fd_forest_pool_idx( pool, ele ) );
}
}

/* Now BFS and clean up children of these orphan heads */
while( FD_UNLIKELY( fd_forest_deque_cnt( queue ) ) ) {
head = fd_forest_pool_ele( pool, fd_forest_deque_pop_head( queue ) );
fd_forest_ele_t * child = fd_forest_pool_ele( pool, head->child );
while( FD_LIKELY( child ) ) {
if( FD_LIKELY( child != new_root_ele ) ) {
fd_forest_deque_push_tail( queue, fd_forest_pool_idx( pool, child ) );
}
child = fd_forest_pool_ele( pool, child->sibling );
}
ulong remove = fd_forest_orphaned_idx_remove( orphaned, &head->slot, null, pool ); /* remove myself */
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clear remove->next too in case there was a map collision (can lead to subtle bugs)

Suggested change
ulong remove = fd_forest_orphaned_idx_remove( orphaned, &head->slot, null, pool ); /* remove myself */
fd_forest_ele_t * remove = fd_forest_orphaned_ele_remove( orphaned, &head->slot, null, pool );
remove->next = idx_null;

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changed to deque for bfs

remove = fd_ulong_if( remove == null, fd_forest_ancestry_idx_remove( ancestry, &head->slot, null, pool ), remove );
fd_forest_pool_ele_release( pool, head ); /* free head */
}
return new_root_ele;
}

Expand Down
16 changes: 12 additions & 4 deletions src/discof/forest/fd_forest.h
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Expand Up @@ -45,7 +45,6 @@

struct __attribute__((aligned(128UL))) fd_forest_ele {
ulong slot; /* map key */
ulong prev; /* internal use by link_orphans */
ulong next; /* internal use by fd_pool, fd_map_chain */
ulong parent; /* pool idx of the parent in the tree */
ulong child; /* pool idx of the left-child */
Expand Down Expand Up @@ -79,6 +78,12 @@ typedef struct fd_forest_ele fd_forest_ele_t;
#define MAP_KEY slot
#include "../../util/tmpl/fd_map_chain.c"

/* Internal use only for BFSing */
#define DEQUE_NAME fd_forest_deque
#define DEQUE_T ulong
#include "../../util/tmpl/fd_deque_dynamic.c"


/* fd_forest_t is the top-level structure that holds the root of
the tree, as well as the memory pools and map structures.

Expand Down Expand Up @@ -111,6 +116,7 @@ struct __attribute__((aligned(128UL))) fd_forest {
ulong ancestry_gaddr; /* wksp_gaddr of fd_forest_ancestry */
ulong frontier_gaddr; /* map of slot to ele (leaf that needs repair) */
ulong orphaned_gaddr; /* map of parent_slot to singly-linked list of ele orphaned by that parent slot */
ulong deque_gaddr; /* wksp gaddr of fd_forest_deque. internal use only for BFSing */
ulong magic; /* ==FD_FOREST_MAGIC */
};
typedef struct fd_forest fd_forest_t;
Expand All @@ -137,13 +143,15 @@ fd_forest_footprint( ulong ele_max ) {
FD_LAYOUT_APPEND(
FD_LAYOUT_APPEND(
FD_LAYOUT_APPEND(
FD_LAYOUT_APPEND(
FD_LAYOUT_INIT,
alignof(fd_forest_t), sizeof(fd_forest_t) ),
fd_fseq_align(), fd_fseq_footprint() ),
fd_forest_pool_align(), fd_forest_pool_footprint( ele_max ) ),
alignof(fd_forest_t), sizeof(fd_forest_t) ),
fd_fseq_align(), fd_fseq_footprint() ),
fd_forest_pool_align(), fd_forest_pool_footprint ( ele_max ) ),
fd_forest_ancestry_align(), fd_forest_ancestry_footprint( ele_max ) ),
fd_forest_frontier_align(), fd_forest_frontier_footprint( ele_max ) ),
fd_forest_orphaned_align(), fd_forest_orphaned_footprint( ele_max ) ),
fd_forest_deque_align(), fd_forest_deque_footprint ( ele_max ) ),
fd_forest_align() );
}

Expand Down
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