changeset 9fa13250abd8 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=9fa13250abd8
description:
SE: Ignore FUTEX_PRIVATE_FLAG of sys_futex
This patch ignores the FUTEX_PRIVATE_FLAG of the sys_futex system call
in SE mode.
With this patch, when sys_futex with the options FUTEX_WAIT_PRIVATE or
FUTEX_WAKE_PRIVATE is emulated, the FUTEX_PRIVATE_FLAG is ignored and
so their behaviours are the regular FUTEX_WAIT and FUTEX_WAKE.
Emulating FUTEX_WAIT_PRIVATE and FUTEX_WAKE_PRIVATE as if they were
non-private is safe from a functional point of view. The
FUTEX_PRIVATE_FLAG does not change the semantics of the futex, it's
just a mechanism to improve performance under certain circunstances
that can be ignored in SE mode.
diffstat:
src/kern/linux/linux.hh | 1 +
src/sim/syscall_emul.hh | 3 ++-
2 files changed, 3 insertions(+), 1 deletions(-)
diffs (31 lines):
diff -r cb942df51335 -r 9fa13250abd8 src/kern/linux/linux.hh
--- a/src/kern/linux/linux.hh Thu Sep 20 17:25:52 2012 -0400
+++ b/src/kern/linux/linux.hh Fri Sep 21 04:51:18 2012 -0400
@@ -225,6 +225,7 @@
static const unsigned TGT_FUTEX_WAKE = 1;
static const unsigned TGT_EAGAIN = 11;
static const unsigned TGT_EWOULDBLOCK = TGT_EAGAIN;
+ static const unsigned TGT_FUTEX_PRIVATE_FLAG = 128;
}; // class Linux
diff -r cb942df51335 -r 9fa13250abd8 src/sim/syscall_emul.hh
--- a/src/sim/syscall_emul.hh Thu Sep 20 17:25:52 2012 -0400
+++ b/src/sim/syscall_emul.hh Fri Sep 21 04:51:18 2012 -0400
@@ -359,6 +359,7 @@
DPRINTF(SyscallVerbose, "In sys_futex: Address=%llx, op=%d, val=%d\n",
uaddr, op, val);
+ op &= ~OS::TGT_FUTEX_PRIVATE_FLAG;
if (op == OS::TGT_FUTEX_WAIT) {
if (timeout != 0) {
@@ -410,7 +411,7 @@
"thread contexts\n", wokenUp);
return wokenUp;
} else {
- warn("sys_futex: op %d is not implemented, just returning...");
+ warn("sys_futex: op %d is not implemented, just returning...", op);
return 0;
}
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