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af7bd80430
This change introduces a new deadlock detector for Cosmo's POSIX threads implementation. Error check mutexes will now track a DAG of nested locks and report EDEADLK when a deadlock is theoretically possible. These will occur rarely, but it's important for production hardening your code. You don't even need to change your mutexes to use the POSIX error check mode because `cosmocc -mdbg` will enable error checking on mutexes by default globally. When cycles are found, an error message showing your demangled symbols describing the strongly connected component are printed and then the SIGTRAP is raised, which means you'll also get a backtrace if you're using ShowCrashReports() too. This new error checker is so low-level and so pure that it's able to verify the relationships of every libc runtime lock, including those locks upon which the mutex implementation depends.
128 lines
4.5 KiB
C
128 lines
4.5 KiB
C
#ifndef COSMOPOLITAN_LIBC_THREAD_POSIXTHREAD_INTERNAL_H_
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#define COSMOPOLITAN_LIBC_THREAD_POSIXTHREAD_INTERNAL_H_
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#include "libc/calls/struct/sched_param.h"
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#include "libc/calls/struct/sigaltstack.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/dll.h"
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#include "libc/runtime/runtime.h"
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#include "libc/thread/pt.internal.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/tls.h"
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#define PT_BLOCKER_EVENT ((atomic_int *)-1)
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COSMOPOLITAN_C_START_
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// LEGAL TRANSITIONS ┌──> TERMINATED ─┐
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// pthread_create ─┬─> JOINABLE ─┴┬─> DETACHED ───┴─> ZOMBIE
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// └──────────────┘
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enum PosixThreadStatus {
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// this is a running thread that needs pthread_join()
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//
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// the following transitions are possible:
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//
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// - kPosixThreadJoinable -> kPosixThreadTerminated if start_routine()
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// returns, or is longjmp'd out of by pthread_exit(), and the thread
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// is waiting to be joined.
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//
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// - kPosixThreadJoinable -> kPosixThreadDetached if pthread_detach()
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// is called on this thread.
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//
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// - kPosixThreadJoinable -> kPosixThreadZombie if another thread
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// calls fork().
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kPosixThreadJoinable,
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// this is a managed thread that'll be cleaned up by the library.
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//
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// the following transitions are possible:
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//
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// - kPosixThreadDetached -> kPosixThreadZombie if start_routine()
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// returns, or is longjmp'd out of by pthread_exit(), and the thread
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// is waiting to be joined.
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//
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// - kPosixThreadDetached -> kPosixThreadZombie if another thread
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// calls fork().
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kPosixThreadDetached,
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// this is a joinable thread that terminated.
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//
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// the following transitions are possible:
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//
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// - kPosixThreadTerminated -> _pthread_free() will happen when
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// pthread_join() is called by the user.
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// - kPosixThreadTerminated -> kPosixThreadZombie will happen when
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// pthread_detach() is called by the user.
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// - kPosixThreadTerminated -> kPosixThreadZombie if another thread
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// calls fork().
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kPosixThreadTerminated,
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// this is a detached thread that terminated.
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//
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// the following transitions are possible:
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//
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// - kPosixThreadZombie -> _pthread_free() will happen whenever
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// convenient, e.g. pthread_create() entry or atexit handler.
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kPosixThreadZombie,
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};
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#define POSIXTHREAD_CONTAINER(e) DLL_CONTAINER(struct PosixThread, list, e)
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typedef struct __locale_struct *locale_t;
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struct PosixThread {
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int pt_flags; // 0x00: see PT_* constants
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atomic_int pt_canceled; // 0x04: thread has bad beliefs
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_Atomic(enum PosixThreadStatus) pt_status;
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atomic_int ptid; // transitions 0 → tid
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atomic_int pt_refs; // prevents decimation
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void *(*pt_start)(void *); // creation callback
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void *pt_arg; // start's parameter
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void *pt_rc; // start's return value
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char *pt_tls; // bottom of tls allocation
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struct CosmoTib *tib; // middle of tls allocation
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struct Dll list; // list of threads
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struct _pthread_cleanup_buffer *pt_cleanup;
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_Atomic(atomic_int *) pt_blocker;
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uint64_t pt_blkmask;
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int64_t pt_event;
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locale_t pt_locale;
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jmp_buf pt_exiter;
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pthread_attr_t pt_attr;
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atomic_bool pt_intoff;
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};
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typedef void (*atfork_f)(void);
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extern struct Dll *_pthread_list;
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extern struct PosixThread _pthread_static;
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extern _Atomic(pthread_key_dtor) _pthread_key_dtor[PTHREAD_KEYS_MAX];
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int _pthread_reschedule(struct PosixThread *) libcesque;
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int _pthread_setschedparam_freebsd(int, int, const struct sched_param *);
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int _pthread_tid(struct PosixThread *) libcesque;
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intptr_t _pthread_syshand(struct PosixThread *) libcesque;
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long _pthread_cancel_ack(void) libcesque;
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void _pthread_decimate(bool) libcesque;
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void _pthread_free(struct PosixThread *) libcesque;
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void _pthread_lock(void) libcesque;
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void _pthread_onfork_child(void) libcesque;
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void _pthread_onfork_parent(void) libcesque;
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void _pthread_onfork_prepare(void) libcesque;
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void _pthread_unlock(void) libcesque;
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void _pthread_zombify(struct PosixThread *) libcesque;
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forceinline pureconst struct PosixThread *_pthread_self(void) {
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return (struct PosixThread *)__get_tls()->tib_pthread;
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}
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forceinline void _pthread_ref(struct PosixThread *pt) {
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atomic_fetch_add_explicit(&pt->pt_refs, 1, memory_order_acq_rel);
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}
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forceinline void _pthread_unref(struct PosixThread *pt) {
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atomic_fetch_sub_explicit(&pt->pt_refs, 1, memory_order_acq_rel);
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}
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COSMOPOLITAN_C_END_
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#endif /* COSMOPOLITAN_LIBC_THREAD_POSIXTHREAD_INTERNAL_H_ */
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