This is a follow up patch to the fix for bug 19329. This adds relaxed
MO atomics to accesses that were previously data races but are now
race conditions, and where relaxed MO is sufficient.
The race conditions all follow the pattern that the write is behind the
dlopen lock, but a read can happen concurrently (e.g. during tls access)
without holding the lock. For slotinfo entries the read value only
matters if it reads from a synchronized write in dlopen or dlclose,
otherwise the related dtv entry is not valid to access so it is fine
to leave it in an inconsistent state. The same applies for
GL(dl_tls_max_dtv_idx) and GL(dl_tls_generation), but there the
algorithm relies on the fact that the read of the last synchronized
write is an increasing value.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
This change forces realignment of the stack pointer in __tls_get_addr, so
that binaries compiled by GCCs older than GCC 4.9:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
continue to work even if vector instructions are used in glibc which
require the ABI stack realignment.
__tls_get_addr_slow is added to handle the slow paths in the default
implementation of__tls_get_addr in elf/dl-tls.c. The new __tls_get_addr
calls __tls_get_addr_slow after realigning the stack. Internal calls
within ld.so go directly to the default implementation of __tls_get_addr
because they do not need stack realignment.
[BZ #21609]
* sysdeps/x86_64/Makefile (sysdep-dl-routines): Add tls_get_addr.
(gen-as-const-headers): Add rtld-offsets.sym.
* sysdeps/x86_64/dl-tls.c: New file.
* sysdeps/x86_64/rtld-offsets.sym: Likwise.
* sysdeps/x86_64/tls_get_addr.S: Likewise.
* sysdeps/x86_64/dl-tls.h: Add multiple inclusion guards.
* sysdeps/x86_64/tlsdesc.sym (TI_MODULE_OFFSET): New.
(TI_OFFSET_OFFSET): Likwise.
