027463d...
by
Michael Jeanson <email address hidden>
Fix: don't use overlapping mmap mappings on Cygwin
The allocation scheme used by the mmap based RCU hash table is to make a
large unaccessible mapping to reserve memory without allocating it.
Then smaller chunks are allocated by overlapping read/write mappings which
do allocate memory. Deallocation is done by an overlapping unaccessible
mapping.
This scheme was tested on Linux, macOS and Solaris. However, on Cygwin the
mmap wrapper is based on the Windows NtMapViewOfSection API which doesn't
support overlapping mappings.
An alternative to the overlapping mappings is to use mprotect to change the
protection on chunks of the large mapping, read/write to allocate and none
to deallocate. This works perfecty on Cygwin and Solaris but on Linux a
call to madvise is also required to deallocate and it just doesn't work on
macOS.
For this reason, we keep to original scheme on all platforms except Cygwin.
d109460...
by
Michael Jeanson <email address hidden>
Fix: Don't override user variables within the build system
Instead use the appropriatly prefixed AM_* variables as to not interfere
when a user variable is passed to a make command. The proper use of flag
variables is documented at :
Fix: uatomic arm32: add missing release barrier before uatomic_xchg
__sync_lock_test_and_set() only imply a release barrier, but
uatomic_xchg() guarantees both acquire and release barrier semantics.
Therefore, add the missing release barrier.
Fix: rcutorture: work-around signal issue on mac os x
Our MacOS X test machine with the following config:
15.6.0 Darwin Kernel Version 15.6.0
root:xnu-3248.60.10~1/RELEASE_X86_64
appears to have issues with liburcu-signal signal being delivered on top
of pthread_cond_wait. It seems to make the thread continue, and
therefore corrupt the rcu_head. Work around this issue by unregistering
the RCU read-side thread immediately after call_rcu (call_rcu needs us
to be registered RCU readers).
