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Eliminate cyclic locks in runtime

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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.
This commit is contained in:
Justine Tunney 2024-12-16 20:51:27 -08:00
parent 26c051c297
commit af7bd80430
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GPG key ID: BE714B4575D6E328
141 changed files with 2094 additions and 1601 deletions
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49
third_party/tz/localtime.c vendored
View file

@ -2,6 +2,10 @@
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8 :vi │
╚─────────────────────────────────────────────────────────────────────────────*/
#define LOCALTIME_IMPLEMENTATION
#include "lock.h"
#include "tzdir.h"
#include "tzfile.h"
#include "private.h"
#include "libc/calls/blockcancel.internal.h"
#include "libc/calls/calls.h"
#include "libc/cxxabi.h"
@ -10,20 +14,15 @@
#include "libc/serialize.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/o.h"
#include "libc/thread/thread.h"
#include "libc/thread/tls.h"
#include "libc/time.h"
#include "libc/inttypes.h"
#include "libc/sysv/consts/ok.h"
#include "libc/runtime/runtime.h"
#include "libc/stdckdint.h"
#include "libc/time.h"
#include "tzdir.h"
#include "tzfile.h"
#include "libc/nt/struct/timezoneinformation.h"
#include "libc/nt/time.h"
#include "libc/dce.h"
#include "private.h"
/* Convert timestamp from time_t to struct tm. */
@ -624,34 +623,10 @@ localtime_windows_init(void)
setenv("TZ", buf, true);
}
static pthread_mutex_t locallock = PTHREAD_MUTEX_INITIALIZER;
static dontinline void
localtime_wipe(void)
{
pthread_mutex_init(&locallock, 0);
}
static dontinline void
localtime_lock(void)
{
pthread_mutex_lock(&locallock);
}
static dontinline void
localtime_unlock(void)
{
pthread_mutex_unlock(&locallock);
}
__attribute__((__constructor__(80)))
textstartup static void
localtime_init(void)
{
localtime_wipe();
pthread_atfork(localtime_lock,
localtime_unlock,
localtime_wipe);
if (IsWindows())
localtime_windows_init();
}
@ -2052,9 +2027,9 @@ localtime_tzset_unlocked(void)
void
tzset(void)
{
localtime_lock();
__localtime_lock();
localtime_tzset_unlocked();
localtime_unlock();
__localtime_unlock();
}
static void
@ -2067,7 +2042,7 @@ static void
localtime_gmtcheck(void)
{
static bool gmt_is_set;
localtime_lock();
__localtime_lock();
if (! gmt_is_set) {
#ifdef ALL_STATE
gmtptr = malloc(sizeof *gmtptr);
@ -2077,7 +2052,7 @@ localtime_gmtcheck(void)
localtime_gmtload(gmtptr);
gmt_is_set = true;
}
localtime_unlock();
__localtime_unlock();
}
/*
@ -2193,11 +2168,11 @@ localsub(struct state const *sp, time_t const *timep, int_fast32_t setname,
static struct tm *
localtime_tzset(time_t const *timep, struct tm *tmp, bool setname)
{
localtime_lock();
__localtime_lock();
if (setname || !lcl_is_set)
localtime_tzset_unlocked();
tmp = localsub(lclptr, timep, setname, tmp);
localtime_unlock();
__localtime_unlock();
return tmp;
}
@ -2834,10 +2809,10 @@ time_t
mktime(struct tm *tmp)
{
time_t t;
localtime_lock();
__localtime_lock();
localtime_tzset_unlocked();
t = mktime_tzname(lclptr, tmp, true);
localtime_unlock();
__localtime_unlock();
return t;
}

12
third_party/tz/lock.h vendored Normal file
View file

@ -0,0 +1,12 @@
#ifndef COSMOPOLITAN_THIRD_PARTY_TZ_LOCK_H_
#define COSMOPOLITAN_THIRD_PARTY_TZ_LOCK_H_
#include "libc/thread/thread.h"
COSMOPOLITAN_C_START_
extern pthread_mutex_t __localtime_lock_obj;
void __localtime_lock(void);
void __localtime_unlock(void);
COSMOPOLITAN_C_END_
#endif /* COSMOPOLITAN_THIRD_PARTY_TZ_LOCK_H_ */