Hi Mark, On 12/07/17 23:32, Mark Rutland wrote: > Currently we define THREAD_SIZE_ORDER dependent on which arm64-specific > page size kconfig symbol was selected. This is unfortunate, as it hides > the relationship between THREAD_SIZE_ORDER and THREAD_SIZE, and makes it > painful more painful than necessary to modify the thread size as we will > need to do for some debug configurations. > > This patch follows arch/metag's approach of consistently defining > THREAD_SIZE in terms of THREAD_SIZE_ORDER. This avoids having ifdefs for > particular page size configurations, and allows us to change a single > definition to change the thread size.
I think this has unintended side effects for 64K page systems. (or at least not yet intended) Today: > #ifdef CONFIG_ARM64_4K_PAGES > #define THREAD_SIZE_ORDER 2 > #elif defined(CONFIG_ARM64_16K_PAGES) > #define THREAD_SIZE_ORDER 0 > #endif Means THREAD_SIZE_ORDER is unset on 64K, and THREAD_SIZE is always: > #define THREAD_SIZE 16384 /kernel/fork.c matches this with its: > # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) [...] > #else [...] > void thread_stack_cache_init(void) > { > thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, > THREAD_SIZE, 0, NULL); > BUG_ON(thread_stack_cache == NULL); > } > #endif To create a kmemcache to share 64K pages as 16K stacks. After this patch: > #define THREAD_SHIFT 14 > > #if THREAD_SHIFT >= PAGE_SHIFT > #define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) > #else > #define THREAD_SIZE_ORDER 0 > #endif Means THREAD_SIZE_ORDER is 0, and: > #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) gives us a 64K THREAD_SIZE. Thanks, James > diff --git a/arch/arm64/include/asm/thread_info.h > b/arch/arm64/include/asm/thread_info.h > index 141f13e9..6d0c59a 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -23,13 +23,17 @@ > > #include <linux/compiler.h> > > -#ifdef CONFIG_ARM64_4K_PAGES > -#define THREAD_SIZE_ORDER 2 > -#elif defined(CONFIG_ARM64_16K_PAGES) > +#include <asm/page.h> > + > +#define THREAD_SHIFT 14 > + > +#if THREAD_SHIFT >= PAGE_SHIFT > +#define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) > +#else > #define THREAD_SIZE_ORDER 0 > #endif > > -#define THREAD_SIZE 16384 > +#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) > #define THREAD_START_SP (THREAD_SIZE - 16) > > #ifndef __ASSEMBLY__ >