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Make improvements to locking

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This change makes pthread_mutex_lock() as fast as _spinlock() by
default. Thread instability issues on NetBSD have been resolved.
Improvements made to gdtoa thread code. Crash reporting will now
synchronize between threads in a slightly better way.
This commit is contained in:
Justine Tunney 2022-06-19 01:13:03 -07:00
parent 25041b8026
commit d5312b60f7
60 changed files with 890 additions and 629 deletions
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54
libc/runtime/clone.c
View file

@ -355,16 +355,15 @@ static wontreturn void NetbsdThreadMain(void *arg, int (*func)(void *arg),
static int CloneNetbsd(int (*func)(void *), char *stk, size_t stksz, int flags,
void *arg, void *tls, size_t tlssz, int *ctid) {
// NetBSD has its own clone() and it works, but it's technically a
// second-class API, intended to help Linux folks migrate to this!
// We put it on the thread's stack, to avoid locking this function
// so its stack doesn't scope. The ucontext struct needs 784 bytes
// second-class API, intended to help Linux folks migrate to this.
bool failed;
int ax, *tid;
intptr_t dx, sp;
static bool once;
static int broken;
struct ucontext_netbsd ctx;
struct ucontext_netbsd *ctx;
static struct ucontext_netbsd netbsd_clone_template;
_Static_assert(sizeof(struct ucontext_netbsd) == 784, "fix assembly");
// memoize arbitrary valid processor state structure
if (!once) {
@ -382,35 +381,48 @@ static int CloneNetbsd(int (*func)(void *), char *stk, size_t stksz, int flags,
return -1;
}
sp = (intptr_t)(stk + stksz);
// allocate memory for child tid
sp -= sizeof(int);
sp = sp & -alignof(int);
tid = (int *)sp;
// align the stack
sp = sp & -16;
// simulate call to misalign stack and ensure backtrace looks good
sp -= 8;
*(intptr_t *)sp = (intptr_t)CloneNetbsd + 1;
// place the giant 784 byte ucontext structure in the red zone!
// it only has to live long enough for the thread to come alive
ctx = (struct ucontext_netbsd *)((sp - sizeof(struct ucontext_netbsd)) &
-alignof(struct ucontext_netbsd));
// pass parameters in process state
memcpy(&ctx, &netbsd_clone_template, sizeof(ctx));
ctx.uc_link = 0;
ctx.uc_mcontext.rbp = 0;
ctx.uc_mcontext.rsp = sp;
ctx.uc_mcontext.rip = (intptr_t)NetbsdThreadMain;
ctx.uc_mcontext.rdi = (intptr_t)arg;
ctx.uc_mcontext.rsi = (intptr_t)func;
ctx.uc_mcontext.rdx = (intptr_t)tid;
ctx.uc_mcontext.rcx = (intptr_t)(flags & CLONE_CHILD_SETTID ? ctid : tid);
ctx.uc_mcontext.r8 = (intptr_t)(flags & CLONE_CHILD_CLEARTID ? ctid : tid);
ctx.uc_flags |= _UC_STACK;
ctx.uc_stack.ss_sp = stk;
ctx.uc_stack.ss_size = stksz;
ctx.uc_stack.ss_flags = 0;
memcpy(ctx, &netbsd_clone_template, sizeof(*ctx));
ctx->uc_link = 0;
ctx->uc_mcontext.rbp = 0;
ctx->uc_mcontext.rsp = sp;
ctx->uc_mcontext.rip = (intptr_t)NetbsdThreadMain;
ctx->uc_mcontext.rdi = (intptr_t)arg;
ctx->uc_mcontext.rsi = (intptr_t)func;
ctx->uc_mcontext.rdx = (intptr_t)tid;
ctx->uc_mcontext.rcx = (intptr_t)(flags & CLONE_CHILD_SETTID ? ctid : tid);
ctx->uc_mcontext.r8 = (intptr_t)(flags & CLONE_CHILD_CLEARTID ? ctid : tid);
ctx->uc_flags |= _UC_STACK;
ctx->uc_stack.ss_sp = stk;
ctx->uc_stack.ss_size = stksz;
ctx->uc_stack.ss_flags = 0;
if (flags & CLONE_SETTLS) {
ctx.uc_flags |= _UC_TLSBASE;
ctx.uc_mcontext._mc_tlsbase = (intptr_t)tls;
ctx->uc_flags |= _UC_TLSBASE;
ctx->uc_mcontext._mc_tlsbase = (intptr_t)tls;
}
// perform the system call
asm volatile(CFLAG_ASM("syscall")
: CFLAG_CONSTRAINT(failed), "=a"(ax), "=d"(dx)
: "1"(__NR__lwp_create), "D"(&ctx), "S"(LWP_DETACHED), "2"(tid)
: "1"(__NR__lwp_create), "D"(ctx), "S"(LWP_DETACHED), "2"(tid)
: "rcx", "r11", "memory");
if (!failed) {
return *tid;