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Merge pull request 'LinuxThreadImpl fixups' (#31716) from blblack/zig:linux-thread-childtid into master

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Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31716
Reviewed-by: Alex Rønne Petersen <alex@alexrp.com>
This commit is contained in:
Alex Rønne Petersen 2026-04-01 11:38:06 +02:00
commit 27611c10f8
2 changed files with 11 additions and 1 deletions
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7
lib/std/Thread.zig
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@ -1147,6 +1147,11 @@ const LinuxThreadImpl = struct {
/// Ported over from musl libc's pthread detached implementation:
/// https://github.com/ifduyue/musl/search?q=__unmapself
fn freeAndExit(self: *ThreadCompletion) noreturn {
// If we do not reset the child_tidptr to null here, the kernel would later write the
// value zero to that address, which is inside the block we're unmapping below, after
// our thread exits. This can sometimes corrupt memory in other mmap blocks from
// unrelated concurrent threads.
_ = linux.set_tid_address(null);
// If a signal were delivered between SYS_munmap and SYS_exit, any installed signal
// handler would immediately segfault due to the stack being unmapped. To avoid this,
// we need to mask all signals before entering the inline asm.
@ -1484,7 +1489,7 @@ const LinuxThreadImpl = struct {
}
// Prepare the TLS segment and prepare a user_desc struct when needed on x86
var tls_ptr = linux.tls.prepareArea(mapped[tls_offset..]);
var tls_ptr = linux.tls.prepareArea(mapped[tls_offset..][0..linux.tls.area_desc.size]);
var user_desc: if (target.cpu.arch == .x86) linux.user_desc else void = undefined;
if (target.cpu.arch == .x86) {
defer tls_ptr = @intFromPtr(&user_desc);

5
lib/std/os/linux.zig
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@ -1584,6 +1584,11 @@ pub fn clone2(flags: u32, child_stack_ptr: usize) usize {
return syscall2(.clone, flags, child_stack_ptr);
}
/// This call cannot fail, and the return value is the caller's thread id
pub fn set_tid_address(tidptr: ?*pid_t) pid_t {
return @intCast(@as(u32, @truncate(syscall1(.set_tid_address, @intFromPtr(tidptr)))));
}
pub fn close(fd: fd_t) usize {
return syscall1(.close, @as(usize, @bitCast(@as(isize, fd))));
}