>>>>> On Thu, 30 Jun 2005 11:50:57 -0400, Dave Johnson <djohnson+linuxmips@xxxxxxxxxxxxxxxxxxxxxx> said: dave> The PC it was trying to lookup is in preempt_schedule_irq(). dave> Without preempt_schedule_irq in mfinfo[] it ended up with the dave> wrong function and then dereferenced a NULL FP. dave> Should this be in mfinfo or am I on the wrong track here? ... dave> Also, __preempt_spin_lock and __preempt_write_lock are nowhere dave> to be found so I had to remove those from the table. Well, The current get_wchan implementation is still problematic because: * Some functions in __sched (and __lock) section are static. * Functions in __lock are not handled. * Maintenance of the struct mips_frame_info mfinfo[] is a pain. * sleep_on*() is deprecated. kernel-janitors people want to remove references for them. I suppose searching a caller of scheduling functions in get_wchan is not necessary. Calling thread_saved_pc() will be enough for most usage. So I posted a patch to simplify things a while ago. http://www.linux-mips.org/cgi-bin/mesg.cgi?a=linux-mips&i=20050126.120916.88699500.nemoto%40toshiba-tops.co.jp And here is a revised patch. diff -u linux-mips/arch/mips/kernel/process.c linux/arch/mips/kernel/process.c --- linux-mips/arch/mips/kernel/process.c 2005-06-21 17:34:10.000000000 +0900 +++ linux/arch/mips/kernel/process.c 2005-07-01 11:15:26.000000000 +0900 @@ -270,47 +270,15 @@ } static struct mips_frame_info { - void *func; - int omit_fp; /* compiled without fno-omit-frame-pointer */ int frame_offset; int pc_offset; -} schedule_frame, mfinfo[] = { - { schedule, 0 }, /* must be first */ - /* arch/mips/kernel/semaphore.c */ - { __down, 1 }, - { __down_interruptible, 1 }, - /* kernel/sched.c */ -#ifdef CONFIG_PREEMPT - { preempt_schedule, 0 }, -#endif - { wait_for_completion, 0 }, - { interruptible_sleep_on, 0 }, - { interruptible_sleep_on_timeout, 0 }, - { sleep_on, 0 }, - { sleep_on_timeout, 0 }, - { yield, 0 }, - { io_schedule, 0 }, - { io_schedule_timeout, 0 }, -#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT) - { __preempt_spin_lock, 0 }, - { __preempt_write_lock, 0 }, -#endif - /* kernel/timer.c */ - { schedule_timeout, 1 }, -/* { nanosleep_restart, 1 }, */ - /* lib/rwsem-spinlock.c */ - { __down_read, 1 }, - { __down_write, 1 }, -}; - -static int mips_frame_info_initialized; -static int __init get_frame_info(struct mips_frame_info *info) +} schedule_frame; +static int __init get_frame_info(struct mips_frame_info *info, void *func) { int i; - void *func = info->func; union mips_instruction *ip = (union mips_instruction *)func; info->pc_offset = -1; - info->frame_offset = info->omit_fp ? 0 : -1; + info->frame_offset = -1; for (i = 0; i < 128; i++, ip++) { /* if jal, jalr, jr, stop. */ if (ip->j_format.opcode == jal_op || @@ -358,26 +326,7 @@ static int __init frame_info_init(void) { - int i, found; - for (i = 0; i < ARRAY_SIZE(mfinfo); i++) - if (get_frame_info(&mfinfo[i])) - return -1; - schedule_frame = mfinfo[0]; - /* bubble sort */ - do { - struct mips_frame_info tmp; - found = 0; - for (i = 1; i < ARRAY_SIZE(mfinfo); i++) { - if (mfinfo[i-1].func > mfinfo[i].func) { - tmp = mfinfo[i]; - mfinfo[i] = mfinfo[i-1]; - mfinfo[i-1] = tmp; - found = 1; - } - } - } while (found); - mips_frame_info_initialized = 1; - return 0; + return get_frame_info(&schedule_frame, schedule); } arch_initcall(frame_info_init); @@ -398,39 +347,12 @@ return ((unsigned long *)t->reg29)[schedule_frame.pc_offset]; } -/* get_wchan - a maintenance nightmare^W^Wpain in the ass ... */ unsigned long get_wchan(struct task_struct *p) { - unsigned long frame, pc; - if (!p || p == current || p->state == TASK_RUNNING) return 0; - if (!mips_frame_info_initialized) - return 0; - pc = thread_saved_pc(p); - - if (!in_sched_functions(pc)) - goto out; - - frame = ((unsigned long *)p->thread.reg30)[schedule_frame.frame_offset]; - do { - int i; - for (i = ARRAY_SIZE(mfinfo) - 1; i >= 0; i--) { - if (pc >= (unsigned long) mfinfo[i].func) - break; - } - if (i < 0) - break; - - if (mfinfo[i].omit_fp) - break; - pc = ((unsigned long *)frame)[mfinfo[i].pc_offset]; - frame = ((unsigned long *)frame)[mfinfo[i].frame_offset]; - } while (in_sched_functions(pc)); - -out: - return pc; + return thread_saved_pc(p); } EXPORT_SYMBOL(get_wchan); --- Atsushi Nemoto
