Fixed potential race-to-sleep condition in cpu_idle(). I hope. If called with interrupts disabled, our __vmwait() actually just returns without servicing it. Let me know if there's any other condition that I've missed... Signed-off-by: Richard Kuo --- arch/hexagon/kernel/init_task.c | 54 +++++++ arch/hexagon/kernel/process.c | 278 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 332 insertions(+) Index: linux-hexagon-kernel/arch/hexagon/kernel/init_task.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-hexagon-kernel/arch/hexagon/kernel/init_task.c 2011-08-24 18:45:48.203877165 -0500 @@ -0,0 +1,54 @@ +/* + * Init task definition + * + * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 and + * only version 2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static struct signal_struct init_signals = INIT_SIGNALS(init_signals); +static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand); + +/* + * Initial thread structure. + * + * We need to make sure that this is 8192-byte aligned due to the + * way process stacks are handled. This is done by making sure + * the linker maps this in the .text segment right after head.S, + * and making head.S ensure the proper alignment. + */ +union thread_union init_thread_union + __attribute__((__section__(".data.init_task"), + __aligned__(THREAD_SIZE))) = { + INIT_THREAD_INFO(init_task) + }; + +/* + * Initial task structure. + * + * All other task structs will be allocated on slabs in fork.c + */ +struct task_struct init_task = INIT_TASK(init_task); +EXPORT_SYMBOL(init_task); Index: linux-hexagon-kernel/arch/hexagon/kernel/process.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-hexagon-kernel/arch/hexagon/kernel/process.c 2011-08-24 18:45:48.203877165 -0500 @@ -0,0 +1,278 @@ +/* + * Process creation support for Hexagon + * + * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 and + * only version 2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +#include +#include +#include +#include +#include +#include + +/* + * Kernel thread creation. The desired kernel function is "wrapped" + * in the kernel_thread_helper function, which does cleanup + * afterwards. + */ +static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *)) +{ + do_exit(fn(arg)); +} + +int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) +{ + struct pt_regs regs; + + memset(®s, 0, sizeof(regs)); + /* + * Yes, we're exploting illicit knowledge of the ABI here. + */ + regs.r00 = (unsigned long) arg; + regs.r01 = (unsigned long) fn; + pt_set_elr(®s, (unsigned long)kernel_thread_helper); + pt_set_kmode(®s); + + return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL); +} +EXPORT_SYMBOL(kernel_thread); + +/* + * Program thread launch. Often defined as a macro in processor.h, + * but we're shooting for a small footprint and it's not an inner-loop + * performance-critical operation. + * + * The Hexagon ABI specifies that R28 is zero'ed before program launch, + * so that gets automatically done here. If we ever stop doing that here, + * we'll probably want to define the ELF_PLAT_INIT macro. + */ +void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) +{ + /* Set to run with user-mode data segmentation */ + set_fs(USER_DS); + /* We want to zero all data-containing registers. Is this overkill? */ + memset(regs, 0, sizeof(*regs)); + /* We might want to also zero all Processor registers here */ + pt_set_usermode(regs); + pt_set_elr(regs, pc); + pt_set_rte_sp(regs, sp); +} + +/* + * Spin, or better still, do a hardware or VM wait instruction + * If hardware or VM offer wait termination even though interrupts + * are disabled. + */ +static void default_idle(void) +{ + __vmwait(); +} + +void (*idle_sleep)(void) = default_idle; + +void cpu_idle(void) +{ + while (1) { + tick_nohz_stop_sched_tick(1); + local_irq_disable(); + while (!need_resched()) { + idle_sleep(); + /* interrupts wake us up, but aren't serviced */ + local_irq_enable(); /* service interrupt */ + local_irq_disable(); + } + tick_nohz_restart_sched_tick(); + schedule(); + } +} + +/* + * Return saved PC of a blocked thread + */ +unsigned long thread_saved_pc(struct task_struct *tsk) +{ + return 0; +} + +/* + * Copy architecture-specific thread state + */ +int copy_thread(unsigned long clone_flags, unsigned long usp, + unsigned long unused, struct task_struct *p, + struct pt_regs *regs) +{ + struct thread_info *ti = task_thread_info(p); + struct hexagon_switch_stack *ss; + struct pt_regs *childregs; + asmlinkage void ret_from_fork(void); + + childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - + sizeof(*childregs)); + + memcpy(childregs, regs, sizeof(*childregs)); + ti->regs = childregs; + + /* + * Establish kernel stack pointer and initial PC for new thread + */ + ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - + sizeof(*ss)); + ss->lr = (unsigned long)ret_from_fork; + p->thread.switch_sp = ss; + + /* If User mode thread, set pt_reg stack pointer as per parameter */ + if (user_mode(childregs)) { + pt_set_rte_sp(childregs, usp); + + /* Child sees zero return value */ + childregs->r00 = 0; + + /* + * The clone syscall has the C signature: + * int [r0] clone(int flags [r0], + * void *child_frame [r1], + * void *parent_tid [r2], + * void *child_tid [r3], + * void *thread_control_block [r4]); + * ugp is used to provide TLS support. + */ + if (clone_flags & CLONE_SETTLS) + childregs->ugp = childregs->r04; + + /* + * Parent sees new pid -- not necessary, not even possible at + * this point in the fork process + * Might also want to set things like ti->addr_limit + */ + } else { + /* + * If kernel thread, resume stack is kernel stack base. + * Note that this is pointer arithmetic on pt_regs * + */ + pt_set_rte_sp(childregs, (unsigned long)(childregs + 1)); + /* + * We need the current thread_info fast path pointer + * set up in pt_regs. The register to be used is + * parametric for assembler code, but the mechanism + * doesn't drop neatly into C. Needs to be fixed. + */ + childregs->THREADINFO_REG = (unsigned long) ti; + } + + /* + * thread_info pointer is pulled out of task_struct "stack" + * field on switch_to. + */ + p->stack = (void *)ti; + + return 0; +} + +/* + * Release any architecture-specific resources locked by thread + */ +void release_thread(struct task_struct *dead_task) +{ +} + +/* + * Free any architecture-specific thread data structures, etc. + */ +void exit_thread(void) +{ +} + +/* + * Some archs flush debug and FPU info here + */ +void flush_thread(void) +{ +} + +/* + * The "wait channel" terminology is archaic, but what we want + * is an identification of the point at which the scheduler + * was invoked by a blocked thread. + */ +unsigned long get_wchan(struct task_struct *p) +{ + unsigned long fp, pc; + unsigned long stack_page; + int count = 0; + if (!p || p == current || p->state == TASK_RUNNING) + return 0; + + stack_page = (unsigned long)task_stack_page(p); + fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; + do { + if (fp < (stack_page + sizeof(struct thread_info)) || + fp >= (THREAD_SIZE - 8 + stack_page)) + return 0; + pc = ((unsigned long *)fp)[1]; + if (!in_sched_functions(pc)) + return pc; + fp = *(unsigned long *) fp; + } while (count++ < 16); + + return 0; +} + +/* + * Borrowed from PowerPC -- basically allow smaller kernel stacks if we + * go crazy with the page sizes. + */ +#if THREAD_SHIFT < PAGE_SHIFT + +static struct kmem_cache *thread_info_cache; + +struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node) +{ + struct thread_info *ti; + + ti = kmem_cache_alloc_node(thread_info_cache, GFP_KERNEL, node); + if (unlikely(ti == NULL)) + return NULL; +#ifdef CONFIG_DEBUG_STACK_USAGE + memset(ti, 0, THREAD_SIZE); +#endif + return ti; +} + +void free_thread_info(struct thread_info *ti) +{ + kmem_cache_free(thread_info_cache, ti); +} + +/* Weak symbol; called by init/main.c */ + +void thread_info_cache_init(void) +{ + thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, + THREAD_SIZE, 0, NULL); + BUG_ON(thread_info_cache == NULL); +} + +#endif /* THREAD_SHIFT < PAGE_SHIFT */ + +/* + * Required placeholder. + */ +int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu) +{ + return 0; +} -- Sent by an employee of the Qualcomm Innovation Center, Inc. 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