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[gdb/symtab] Make per_cu->unit_type atomic

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With gdb with -fsanitize=thread and test-case gdb.ada/array_bounds.exp, I run
into a data race between:
...
  Read of size 1 at 0x7b2000025f0f by main thread:
    #0 packed<dwarf_unit_type, 1ul>::operator dwarf_unit_type() const packed.h:54
    #1 dwarf2_per_cu_data::set_unit_type(dwarf_unit_type) read.h:339
...
and:
...
  Previous write of size 1 at 0x7b2000025f0f by thread T3:
    #0 dwarf2_per_cu_data::set_unit_type(dwarf_unit_type) read.h:341
...

Fix this by making per_cu->unit_type atomic.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29286
This commit is contained in:
Tom de Vries
2022-07-14 08:19:00 +02:00
parent 4f92e10cda
commit b35bd7d552
1 changed files with 14 additions and 9 deletions
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23
gdb/dwarf2/read.h
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@ -178,7 +178,7 @@ public:
private:
/* The unit type of this CU. */
packed<dwarf_unit_type, 1> m_unit_type = (dwarf_unit_type) 0;
std::atomic<packed<dwarf_unit_type, 1>> m_unit_type {(dwarf_unit_type)0};
/* The language of this CU. */
packed<language, LANGUAGE_BYTES> m_lang = language_unknown;
@ -329,19 +329,24 @@ public:
dwarf_unit_type unit_type (bool strict_p = true) const
{
dwarf_unit_type ut = m_unit_type.load ();
if (strict_p)
gdb_assert (m_unit_type != 0);
return m_unit_type;
gdb_assert (ut != 0);
return ut;
}
void set_unit_type (dwarf_unit_type unit_type)
{
if (m_unit_type == 0)
/* Set if not set already. */
m_unit_type = unit_type;
else
/* If already set, verify that it's the same value. */
gdb_assert (m_unit_type == unit_type);
/* Set if not set already. */
packed<dwarf_unit_type, 1> nope = (dwarf_unit_type)0;
if (m_unit_type.compare_exchange_strong (nope, unit_type))
return;
/* If already set, verify that it's the same value. */
nope = unit_type;
if (m_unit_type.compare_exchange_strong (nope, unit_type))
return;
gdb_assert_not_reached ();
}
enum language lang (bool strict_p = true) const