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19.5. Bug Fixes

The ld linker generates correct dynamic executables

Previously, the ld linker failed to create correct dynamic executables and terminated when invoked by the Go language compiler go on the 64-bit ARM architecture. The linker has been updated to correctly handle copy relocations. As a result, the linker no longer fails in the described situation. (BZ#1430743)

The ld linker generates correct dynamic relocations for constant data

Previously, the ld linker generated an incorrect kind of dynamic relocations for constant data shared between a library and executable on the 64-bit ARM architecture. As a consequence, the produced executable files wasted resources and terminated unexpectedly when the shared data was accessed. The linker has been updated to generate correct dynamic relocations, and the described problem no longer occurs. (BZ#1452170)

qrwlock is now enabled for 64-bit ARM systems

This update introduces the qrwlock queued read-write lock for 64-bit ARM systems. The implementation of this mechanism improves performance and prevents lock starvation by ensuring fair handling of multiple CPUs competing for the global task lock. This change also resolves a known issue tracked in Red Hat Bugzilla #1454844, which was present in earlier releases and which caused soft lockups under heavy load.
Note that any kernel modules built for previous versions of Red Hat Enterprise Linux 7 for ARM (against the kernel-alt packages) must be rebuilt against the updated kernel.

CMA disabled by default

On 64-bit ARM Red Hat Enterprise Linux systems with memory limited to 1G or below, the Contiguous Memory Allocator (CMA) consumed large amount of memory, thus leaving insufficient memory for the rest of the kernel. Consequently, the out-of-memory (OOM) condition sometimes occurred in the kernel or certain user-space applications, such as Shared Memory in Linux (SHM)(/dev/shm).
The CMA support in the Red Hat Enterprise Linux kernel is now disabled by default for all architectures, and CMA no longer causes OOM.(BZ#1519317)