Review Board 2.0.15


Ignore FUTEX_PRIVATE_FLAG of sys_futex in SE mode

Review Request #1428 - Created Sept. 20, 2012 and submitted - Latest diff uploaded

Information
Lluc Alvarez
gem5
Reviewers
Default
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.