-/* Copyright (C) 2008, 2009, 2011, 2012 Free Software Foundation, Inc.
+/* Copyright (C) 2008-2018 Free Software Foundation, Inc.
Contributed by Richard Henderson <rth@redhat.com>.
This file is part of the GNU Transactional Memory Library (libitm).
namespace GTM HIDDEN {
-
-void
-gtm_undolog::rollback (size_t until_size)
+// This function needs to be noinline because we need to prevent that it gets
+// inlined into another function that calls further functions. This could
+// break our assumption that we only call memcpy and thus only need to
+// additionally protect the memcpy stack (see the hack in mask_stack_bottom()).
+// Even if that isn't an issue because those other calls don't happen during
+// copying, we still need mask_stack_bottom() to be called "close" to the
+// memcpy in terms of stack frames, so just ensure that for now using the
+// noinline.
+void __attribute__((noinline))
+gtm_undolog::rollback (gtm_thread* tx, size_t until_size)
{
size_t i, n = undolog.size();
+ void *top = mask_stack_top(tx);
+ void *bot = mask_stack_bottom(tx);
if (n > 0)
{
size_t len = undolog[i];
size_t words = (len + sizeof(gtm_word) - 1) / sizeof(gtm_word);
i -= words;
- __builtin_memcpy (ptr, &undolog[i], len);
+ // Filter out any updates that overlap the libitm stack. We don't
+ // bother filtering out just the overlapping bytes because we don't
+ // merge writes and thus any overlapping write is either bogus or
+ // would restore data on stack frames that are not in use anymore.
+ // FIXME The memcpy can/will end up as another call but we
+ // calculated BOT based on the current function. Can we inline or
+ // reimplement this without too much trouble due to unaligned calls
+ // and still have good performance, so that we can remove the hack
+ // in mask_stack_bottom()?
+ if (likely(ptr > top || (uint8_t*)ptr + len <= bot))
+ __builtin_memcpy (ptr, &undolog[i], len);
}
+ undolog.set_size(until_size);
}
}