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Avoid race condition manipulating heap when goroutine exits. 

From-SVN: r170758
This commit is contained in:
Ian Lance Taylor 2011-03-07 21:56:40 +00:00
parent 457186f6d5
commit 691a924baf
1 changed files with 17 additions and 10 deletions
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27
libgo/runtime/go-go.c
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@ -92,18 +92,15 @@ remove_current_thread (void)
if (list_entry->next != NULL) if (list_entry->next != NULL)
list_entry->next->prev = list_entry->prev; list_entry->next->prev = list_entry->prev;
/* This will look runtime_mheap as needed. */
runtime_MCache_ReleaseAll (mcache); runtime_MCache_ReleaseAll (mcache);
/* As soon as we release this look, a GC could run. Since this /* This should never deadlock--there shouldn't be any code that
thread is no longer on the list, the GC will not find our M holds the runtime_mheap lock when locking __go_thread_ids_lock.
structure, so it could get freed at any time. That means that We don't want to do this after releasing __go_thread_ids_lock
any code from here to thread exit must not assume that the m is because it will mean that the garbage collector might run, and
valid. */ the garbage collector does not try to lock runtime_mheap in all
m = NULL; cases since it knows it is running single-threaded. */
i = pthread_mutex_unlock (&__go_thread_ids_lock);
__go_assert (i == 0);
runtime_lock (&runtime_mheap); runtime_lock (&runtime_mheap);
mstats.heap_alloc += mcache->local_alloc; mstats.heap_alloc += mcache->local_alloc;
mstats.heap_objects += mcache->local_objects; mstats.heap_objects += mcache->local_objects;
@ -111,6 +108,16 @@ remove_current_thread (void)
runtime_FixAlloc_Free (&runtime_mheap.cachealloc, mcache); runtime_FixAlloc_Free (&runtime_mheap.cachealloc, mcache);
runtime_unlock (&runtime_mheap); runtime_unlock (&runtime_mheap);
/* As soon as we release this look, a GC could run. Since this
thread is no longer on the list, the GC will not find our M
structure, so it could get freed at any time. That means that
any code from here to thread exit must not assume that m is
valid. */
m = NULL;
i = pthread_mutex_unlock (&__go_thread_ids_lock);
__go_assert (i == 0);
free (list_entry); free (list_entry);
} }