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fast-import: Avoid infinite loop after reset 

Johannes Sixt noticed that a 'reset' command applied to a branch that
is already active in the branch LRU cache can cause fast-import to
relink the same branch into the LRU cache twice.  This will cause
the LRU cache to contain a cycle, making unload_one_branch run in an
infinite loop as it tries to select the oldest branch for eviction.

I have trivially fixed the problem by adding an active bit to
each branch object; this bit indicates if the branch is already
in the LRU and allows us to avoid trying to add it a second time.
Converting the pack_id field into a bitfield makes this change take
up no additional memory.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
This commit is contained in:
Shawn O. Pearce 2007-03-05 12:31:09 -05:00
parent 7193db3685
commit 734c91f9e2
1 changed files with 11 additions and 5 deletions
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16
fast-import.c
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@ -220,7 +220,8 @@ struct branch
const char *name;
struct tree_entry branch_tree;
uintmax_t last_commit;
unsigned int pack_id;
unsigned active : 1;
unsigned pack_id : PACK_ID_BITS;
unsigned char sha1[20];
};
@ -528,6 +529,7 @@ static struct branch *new_branch(const char *name)
b->table_next_branch = branch_table[hc];
b->branch_tree.versions[0].mode = S_IFDIR;
b->branch_tree.versions[1].mode = S_IFDIR;
b->active = 0;
b->pack_id = MAX_PACK_ID;
branch_table[hc] = b;
branch_count++;
@ -1547,6 +1549,7 @@ static void unload_one_branch(void)
e = active_branches;
active_branches = e->active_next_branch;
}
e->active = 0;
e->active_next_branch = NULL;
if (e->branch_tree.tree) {
release_tree_content_recursive(e->branch_tree.tree);
@ -1559,10 +1562,13 @@ static void unload_one_branch(void)
static void load_branch(struct branch *b)
{
load_tree(&b->branch_tree);
b->active_next_branch = active_branches;
active_branches = b;
cur_active_branches++;
branch_load_count++;
if (!b->active) {
b->active = 1;
b->active_next_branch = active_branches;
active_branches = b;
cur_active_branches++;
branch_load_count++;
}
}
static void file_change_m(struct branch *b)