| Message ID | 20190709092049.13771-2-richard.henderson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tcg: Fix mmap_lock assertion failure, take 2 | expand |
Richard Henderson <richard.henderson@linaro.org> writes: > We have some potential race conditions vs our user-exec signal > handler that will be solved with this barrier. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> > --- > include/qemu/atomic.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h > index a6ac188188..f9cd24c899 100644 > --- a/include/qemu/atomic.h > +++ b/include/qemu/atomic.h > @@ -88,6 +88,13 @@ > #define smp_read_barrier_depends() barrier() > #endif > > +/* > + * A signal barrier forces all pending local memory ops to be observed before > + * a SIGSEGV is delivered to the *same* thread. In practice this is exactly > + * the same as barrier(), but since we have the correct builtin, use it. > + */ > +#define signal_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST) > + > /* Sanity check that the size of an atomic operation isn't "overly large". > * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not > * want to use them because we ought not need them, and this lets us do a > @@ -308,6 +315,10 @@ > #define smp_read_barrier_depends() barrier() > #endif > > +#ifndef signal_barrier > +#define signal_barrier() barrier() > +#endif > + > /* These will only be atomic if the processor does the fetch or store > * in a single issue memory operation > */ -- Alex Bennée
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index a6ac188188..f9cd24c899 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -88,6 +88,13 @@ #define smp_read_barrier_depends() barrier() #endif +/* + * A signal barrier forces all pending local memory ops to be observed before + * a SIGSEGV is delivered to the *same* thread. In practice this is exactly + * the same as barrier(), but since we have the correct builtin, use it. + */ +#define signal_barrier() __atomic_signal_fence(__ATOMIC_SEQ_CST) + /* Sanity check that the size of an atomic operation isn't "overly large". * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not * want to use them because we ought not need them, and this lets us do a @@ -308,6 +315,10 @@ #define smp_read_barrier_depends() barrier() #endif +#ifndef signal_barrier +#define signal_barrier() barrier() +#endif + /* These will only be atomic if the processor does the fetch or store * in a single issue memory operation */
We have some potential race conditions vs our user-exec signal handler that will be solved with this barrier. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- include/qemu/atomic.h | 11 +++++++++++ 1 file changed, 11 insertions(+) -- 2.17.1