That'll do it. My patch wasn't enough. I added some sanity checks to get_wchan and it hit one while running overnight. The task being examined transitioned from !TASK_RUNNING to TASK_RUNNING while it was being examined. Doh! Definately not SMP/preempt safe as written today. -- Dave Johnson Starent Networks Atsushi Nemoto writes: > >>>>> 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
