mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-06-27 14:58:30 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Always initialize thread local storage

Browse source 
We had previously not enabled TLS in MODE=tiny in order to keep the
smallest example programs (e.g. life.com) just 16kb in size. But it
was error prone doing that, so now we just always enable it because
this change uses hacks to ensure it won't increase life.com's size.

This change also fixes a bug on NetBSD, where signal handlers would
break thread local storage if SA_SIGINFO was being used. This looks
like it might be a bug in NetBSD, but it's got a simple workaround.
This commit is contained in:
Justine Tunney 2022-07-18 22:26:11 -07:00
parent 057e8f5b54
commit 69f4152f38
33 changed files with 174 additions and 123 deletions
Download patch file Download diff file Expand all files Collapse all files

23
libc/runtime/clone.c
View file

@ -565,21 +565,9 @@ static int CloneLinux(int (*func)(void *arg, int tid), char *stk, size_t stksz,
* either terminated or has finished using its stack memory
*
* - `CLONE_SETTLS` is needed if you intend to specify the `tls`
* argument, which provides a fast-path solution for changing the
* appropriate TLS segment register within the child thread. The
* child thread may then obtain a reference to the TIB address you
* supplied, by calling __get_tls(). Your C library holds certain
* expectations about the layout of your Thread Information Block
* (TIB), which are all documented by __initialize_tls(). That
* function can be used to initialize the first positive 64 bytes
* of your TLS allocation, which is the memory Cosmopolitan Libc
* wants for itself (and negative addresses are reserved by the
* GNU Linker). Using this flag will transition the C runtime to a
* `__tls_enabled` state automatically. If you use TLS for just
* one thread, then you must be specify TLS for ALL THREADS. It's
* a good idea to do that since TLS can offer considerable (i.e.
* multiple orders of a magnitude) performance improvement for
* TID-dependent C library services, e.g. recursive mutexes.
* argument, which after thread creation may be accessed using
* __get_tls(). Doing this means that `errno`, gettid(), etc.
* correctly work. Caveat emptor if you choose not to do this.
*
* @param arg is passed as an argument to `func` in the child thread
* @param tls may be used to set the thread local storage segment;
@ -594,8 +582,9 @@ int clone(void *func, void *stk, size_t stksz, int flags, void *arg, int *ptid,
int rc;
struct CloneArgs *wt;
if (flags & CLONE_SETTLS) __enable_tls();
if (flags & CLONE_THREAD) __enable_threads();
if (flags & CLONE_THREAD) {
__enable_threads();
}
if (!func) {
rc = einval();