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thread_sync.c (rb_mutex_t): eliminate fork_gen

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The true bug fork_gen was hiding was rb_mutex_abandon_locking_mutex
failing to unconditionally clear the waitq of mutexes it was
waiting on.  So we fix rb_mutex_abandon_locking_mutex, instead,
and eliminate rb_mutex_cleanup_keeping_mutexes.

This commit was tested heavily on a single-core Pentium-M which
was my most reliable reproducer of the "crash.rb" script from
[Bug #15383]

[Bug #14578] [Bug #15383]

Note: [Bug #15430] turned out to be an entirely different
problem: RLIMIT_NPROC limit was hit on the CI VMs.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66489 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
normal 2018-12-22 01:41:18 +00:00
parent 5072f03741
commit 0fd53f519f
2 changed files with 1 additions and 41 deletions
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1
thread.c
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@ -4449,7 +4449,6 @@ rb_thread_atfork(void)
rb_thread_t *th = GET_THREAD(); rb_thread_t *th = GET_THREAD();
rb_thread_atfork_internal(th, terminate_atfork_i); rb_thread_atfork_internal(th, terminate_atfork_i);
th->join_list = NULL; th->join_list = NULL;
rb_mutex_cleanup_keeping_mutexes(th);
rb_fiber_atfork(th); rb_fiber_atfork(th);
/* We don't want reproduce CVE-2003-0900. */ /* We don't want reproduce CVE-2003-0900. */

41
thread_sync.c
View File

@ -45,17 +45,6 @@ typedef struct rb_mutex_struct {
rb_thread_t *th; rb_thread_t *th;
struct rb_mutex_struct *next_mutex; struct rb_mutex_struct *next_mutex;
struct list_head waitq; /* protected by GVL */ struct list_head waitq; /* protected by GVL */
/*
* FIXME: belt-and-suspenders redundancy. This field should NOT
* be necessary at all if:
* - rb_mutex_cleanup_keeping_mutexes
* - rb_mutex_abandon_keeping_mutexes
* - rb_mutex_abandon_locking_mutex
* are all correct, but I suspect one of them is buggy.
* [Bug #15383] [Bug #15430]
*/
rb_serial_t fork_gen;
} rb_mutex_t; } rb_mutex_t;
#if defined(HAVE_WORKING_FORK) #if defined(HAVE_WORKING_FORK)
@ -132,17 +121,9 @@ static rb_mutex_t *
mutex_ptr(VALUE obj) mutex_ptr(VALUE obj)
{ {
rb_mutex_t *mutex; rb_mutex_t *mutex;
rb_serial_t fork_gen = GET_VM()->fork_gen;
TypedData_Get_Struct(obj, rb_mutex_t, &mutex_data_type, mutex); TypedData_Get_Struct(obj, rb_mutex_t, &mutex_data_type, mutex);
/* FIXME: remove (see comment at rb_mutex_t definition) */
if (mutex->fork_gen != fork_gen) {
/* forked children can't reach into parent thread stacks */
mutex->fork_gen = fork_gen;
list_head_init(&mutex->waitq);
}
return mutex; return mutex;
} }
@ -428,8 +409,7 @@ rb_mutex_abandon_locking_mutex(rb_thread_t *th)
if (th->locking_mutex) { if (th->locking_mutex) {
rb_mutex_t *mutex = mutex_ptr(th->locking_mutex); rb_mutex_t *mutex = mutex_ptr(th->locking_mutex);
if (mutex->th == th) list_head_init(&mutex->waitq);
rb_mutex_abandon_all(mutex);
th->locking_mutex = Qfalse; th->locking_mutex = Qfalse;
} }
} }
@ -447,25 +427,6 @@ rb_mutex_abandon_all(rb_mutex_t *mutexes)
list_head_init(&mutex->waitq); list_head_init(&mutex->waitq);
} }
} }
/*
* All other threads are dead in the a new child process, so waitqs
* contain references to dead threads which we need to clean up
*/
static void
rb_mutex_cleanup_keeping_mutexes(const rb_thread_t *current_thread)
{
rb_mutex_t *mutex = current_thread->keeping_mutexes;
rb_serial_t fork_gen = current_thread->vm->fork_gen;
while (mutex) {
/* FIXME: remove (see comment at rb_mutex_t definition) */
mutex->fork_gen = fork_gen;
list_head_init(&mutex->waitq);
mutex = mutex->next_mutex;
}
}
#endif #endif
static VALUE static VALUE