On Tue, Feb 22, 2022 at 02:01:46PM +0000, Stefan Hajnoczi wrote: > v5: > - Added explicit "#include "qemu/coroutine-tls.h" in patch 4 [Philippe] > - Updated patch 1 commit description and comments to describe the current > noinline plus asm volatile approach [Peter] > v4: > - Dropped '[RFC]'. > - Dropped inline asm for now. -fPIC versions of the code are missing and I > hit several issues including a clang LTO bug where thread local variables > are > incorrectly discarded because inline asm is not analyzed to find symbol > dependencies (Serge Guelton is aware). > - Fixed CI failures. > v3: > - Added __attribute__((weak)) to get_ptr_*() [Florian] > - Replace rdfsbase with mov %%fs:0,%0 [Florian] > > This patch series solves the coroutines TLS problem. Coroutines re-entered > from > another thread sometimes see stale TLS values. This happens because compilers > may cache values across yield points, so a value from the previous thread will > be used when the coroutine is re-entered in another thread. > > Serge Guelton developed a portable technique, see the first patch for details. > > I have audited all __thread variables in QEMU and converted those that can be > used from coroutines. Most actually look safe to me. > > Stefan Hajnoczi (4): > tls: add macros for coroutine-safe TLS variables > util/async: replace __thread with QEMU TLS macros > rcu: use coroutine TLS macros > cpus: use coroutine TLS macros for iothread_locked > > include/qemu/coroutine-tls.h | 165 +++++++++++++++++++++++++++++++++++ > include/qemu/rcu.h | 7 +- > softmmu/cpus.c | 9 +- > tests/unit/rcutorture.c | 10 +-- > tests/unit/test-rcu-list.c | 4 +- > util/async.c | 12 +-- > util/rcu.c | 10 +-- > 7 files changed, 193 insertions(+), 24 deletions(-) > create mode 100644 include/qemu/coroutine-tls.h
Ping. Stefan
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