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util: avoid using thread_local variable that has a destructor

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Store the thread name in a `thread_local` variable of type `char[]`
instead of `std::string`. This avoids calling the destructor when
the thread exits. This is a workaround for
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278701

For type-safety, return `std::string` from
`util::ThreadGetInternalName()` instead of `char[]`.

As a side effect of this change, we no longer store a reference
to a `thread_local` variable in `CLockLocation`. This was
dangerous because if the thread quits while the reference still
exists (in the global variable `lock_data`, see inside `GetLockData()`)
then the reference will become dangling.
This commit is contained in:
Vasil Dimov
2024-05-13 16:57:03 +02:00
parent b94061902e
commit d35ba1b3f1
4 changed files with 27 additions and 21 deletions
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31
src/util/threadnames.cpp
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@@ -4,6 +4,7 @@
#include <config/bitcoin-config.h> // IWYU pragma: keep
#include <cstring>
#include <string>
#include <thread>
#include <utility>
@@ -40,27 +41,37 @@ static void SetThreadName(const char* name)
// global.
#if defined(HAVE_THREAD_LOCAL)
static thread_local std::string g_thread_name;
const std::string& util::ThreadGetInternalName() { return g_thread_name; }
/**
* The name of the thread. We use char array instead of std::string to avoid
* complications with running a destructor when the thread exits. Avoid adding
* other thread_local variables.
* @see https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278701
*/
static thread_local char g_thread_name[128]{'\0'};
std::string util::ThreadGetInternalName() { return g_thread_name; }
//! Set the in-memory internal name for this thread. Does not affect the process
//! name.
static void SetInternalName(std::string name) { g_thread_name = std::move(name); }
static void SetInternalName(const std::string& name)
{
const size_t copy_bytes{std::min(sizeof(g_thread_name) - 1, name.length())};
std::memcpy(g_thread_name, name.data(), copy_bytes);
g_thread_name[copy_bytes] = '\0';
}
// Without thread_local available, don't handle internal name at all.
#else
static const std::string empty_string;
const std::string& util::ThreadGetInternalName() { return empty_string; }
static void SetInternalName(std::string name) { }
std::string util::ThreadGetInternalName() { return ""; }
static void SetInternalName(const std::string& name) { }
#endif
void util::ThreadRename(std::string&& name)
void util::ThreadRename(const std::string& name)
{
SetThreadName(("b-" + name).c_str());
SetInternalName(std::move(name));
SetInternalName(name);
}
void util::ThreadSetInternalName(std::string&& name)
void util::ThreadSetInternalName(const std::string& name)
{
SetInternalName(std::move(name));
SetInternalName(name);
}