[PULL 03/11] bsd-user: Flag shared memory as needing atomics

[Warner Losh <imp@bsdimp.com>]

Catch up with linux-user 228168cbb7c:
    Signal the translator to use host atomic instructions for
    guest operations, insofar as it is possible.  This is the
    best we can do to allow the guest to interact atomically
    with other processes.

as well as subsequent tweaks and adjustmentst for bsd-user's code
structure (we don't have one exit path linux-user does and could frankly
stand to resturcture a bit to match the evolved code in linux-user). On
non-private mmap(2) sharing and all successful shmat(2) calls we tell
tcg that we're in a parallel context, which changes how it does atomics.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/bsd-mem.h | 8 ++++++++
 bsd-user/mmap.c    | 9 +++++++++
 2 files changed, 17 insertions(+)

diff --git a/bsd-user/bsd-mem.h b/bsd-user/bsd-mem.h
index 3086143d40..65270e2cdf 100644
--- a/bsd-user/bsd-mem.h
+++ b/bsd-user/bsd-mem.h
@@ -389,6 +389,14 @@ static inline abi_long do_bsd_shmat(int shmid, abi_ulong shmaddr, int shmflg)
         }
     }
 
+    /*
+     * We're mapping shared memory, so ensure we generate code for parallel
+     * execution and flush old translations.  This will work up to the level
+     * supported by the host -- anything that requires EXCP_ATOMIC will not
+     * be atomic with respect to an external process.
+     */
+    begin_parallel_context(thread_cpu);
+
     return raddr;
 }
 
diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
index fe77eceb48..548b4824df 100644
--- a/bsd-user/mmap.c
+++ b/bsd-user/mmap.c
@@ -662,6 +662,15 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
     printf("\n");
 #endif
     mmap_unlock();
+    /*
+     * If we're mapping shared memory, ensure we generate code for parallel
+     * execution and flush old translations.  This will work up to the level
+     * supported by the host -- anything that requires EXCP_ATOMIC will not
+     * be atomic with respect to an external process.
+     */
+    if ((flags & MAP_TYPE) != MAP_PRIVATE) {
+        begin_parallel_context(thread_cpu);
+    }
     return start;
 fail:
     mmap_unlock();
-- 
2.55.0