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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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36
libc/log/oncrash.c
View file

@ -26,6 +26,7 @@
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/lockcmpxchg.h"
#include "libc/intrin/lockcmpxchgp.h"
#include "libc/log/backtrace.internal.h"
#include "libc/log/gdb.h"
#include "libc/log/internal.h"
@ -262,15 +263,22 @@ static wontreturn relegated noinstrument void __minicrash(int sig,
* simply print addresses which may be cross-referenced using objdump.
*
* This function never returns, except for traps w/ human supervision.
*
* @threadsafe
* @vforksafe
*/
relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
intptr_t rip;
int me, owner;
int gdbpid, err;
static bool noreentry, notpossible;
static int sync;
static bool notpossible;
STRACE("__oncrash rip %x", ctx->uc_mcontext.rip);
--__ftrace;
--__strace;
if (_lockcmpxchg(&noreentry, false, true)) {
owner = 0;
me = gettid();
if (_lockcmpxchgp(&sync, &owner, me)) {
if (!__vforked) {
rip = ctx ? ctx->uc_mcontext.rip : 0;
err = errno;
@ -292,20 +300,30 @@ relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
__restorewintty();
_Exit(128 + sig);
}
sync = 0;
} else {
sync = 0;
__minicrash(sig, si, ctx, "WHILE VFORKED");
}
} else if (sig == SIGTRAP) {
/* chances are IsDebuggerPresent() confused strace w/ gdb */
// chances are IsDebuggerPresent() confused strace w/ gdb
goto ItsATrap;
} else if (_lockcmpxchg(&notpossible, false, true)) {
__minicrash(sig, si, ctx, "WHILE CRASHING");
} else {
for (;;) {
asm("ud2");
} else if (owner == me) {
// we crashed while generating a crash report
if (_lockcmpxchg(&notpossible, false, true)) {
__minicrash(sig, si, ctx, "WHILE CRASHING");
} else {
// somehow __minicrash() crashed not possible
for (;;) {
asm("ud2");
}
}
} else {
// multiple threads have crashed
// kill current thread assuming process dies soon
// TODO(jart): It'd be nice to report on all threads.
_Exit1(8);
}
noreentry = false;
ItsATrap:
++__strace;
++__ftrace;