Hi All, This series is to address the problem with RCU synchronization occurring, possibly relatively often, inside of acpi_ex_system_memory_space_handler(), when the namespace and interpreter mutexes are held. The basic idea is to avoid the actual unmapping of memory in acpi_ex_system_memory_space_handler() by making it take the advantage of the reference counting of memory mappings utilized by the OSL layer in Linux. The basic assumption in patch [1/3] is that if the special ACPI_OS_MAP_MEMORY_FAST_PATH() macro is present, it can be used to increment the reference counter of a known-existing memory mapping in the OS layer which then is dropped by the subsequent acpi_os_unmap_memory() without unmapping the address range at hand. That can be utilized by acpi_ex_system_memory_space_handler() to prevent the reference counters of all mappings used by it from dropping down to 0 (which also prevents the address ranges associated with them from being unmapped) so that they can be unmapped later (specifically, at the operation region deactivation time). Patch [2/3] defers the unmapping even further, until the namespace and interpreter mutexes are released, to avoid invoking the RCU synchronization under theses mutexes. Finally, patch [3/3] changes the OS layer in Linux to provide the ACPI_OS_MAP_MEMORY_FAST_PATH() macro. Note that if this macro is not defined, the code works the way it used to. The series is available from the git branch at git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \ acpica-osl for easier testing. Cheers, Rafael
