https://sourceware.org/bugzilla/show_bug.cgi?id=26930
Bug ID: 26930
Summary: tsearch/tfind tree caches need locking
Product: elfutils
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: libdw
Assignee: unassigned at sourceware dot org
Reporter: mark at klomp dot org
CC: elfutils-devel at sourceware dot org
Target Milestone: ---
libdw uses various search trees as (lazy) caches.
Specifically struct Dwarf has:
/* Search tree for the CUs. */
void *cu_tree;
Dwarf_Off next_cu_offset;
/* Search tree and sig8 hash table for .debug_types type units. */
void *tu_tree;
Dwarf_Off next_tu_offset;
Dwarf_Sig8_Hash sig8_hash;
/* Search tree for split Dwarf associated with CUs in this debug. */
void *split_tree;
/* Search tree for .debug_macro operator tables. */
void *macro_ops;
/* Search tree for decoded .debug_line units. */
void *files_lines;
struct Dwarf_CU has:
/* Known location lists. */
void *locs;
struct Dwarf_CFI_s has:
/* Search tree for the CIEs, indexed by CIE_pointer (section offset). */
void *cie_tree;
/* Search tree for the FDEs, indexed by PC address. */
void *fde_tree;
/* Search tree for parsed DWARF expressions, indexed by raw pointer. */
void *expr_tree;
struct Dwfl_Module has:
void *lazy_cu_root; /* Table indexed by Dwarf_Off of CU. */
When used in a concurrent program they need to be read locked when searched
(with tfind) and write locked when updating (with tsearch).
See several backtraces in bug #26921 which describes a different concurrent
unsafe update mechanism.
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