Hi, sorry not to do a proper threaded reply, but I can't find an mbox of the relevant message (or know another good way to do it). Well I don't presume to know the ia64 unwind code, however from the sounds of it, we _might_ be able to get away with simply blocking the task from running at the scheduler, during the unwind? Note this requires we have interrupts disabled and the rq lock held, so it may not work if the unwinder does anything nontrivial... Longer term, it seems better to make the unwinder more robust, but maybe this gives us a fix until then? Just an idea (untested!) --- Index: linux-2.6/arch/ia64/kernel/process.c =================================================================== --- linux-2.6.orig/arch/ia64/kernel/process.c +++ linux-2.6/arch/ia64/kernel/process.c @@ -760,7 +760,9 @@ unsigned long get_wchan (struct task_struct *p) { struct unw_frame_info info; + unsigned long flags; unsigned long ip; + unsigned long ret = 0; int count = 0; /* @@ -771,15 +773,24 @@ get_wchan (struct task_struct *p) * gracefully if the process wasn't really blocked after all. * --davidm 99/12/15 */ + if (!lock_blocked_task(p, &flags)) + goto out; + unw_init_from_blocked_task(&info, p); do { if (unw_unwind(&info) < 0) - return 0; + goto unlock; unw_get_ip(&info, &ip); - if (!in_sched_functions(ip)) - return ip; + if (!in_sched_functions(ip)) { + ret = ip; + goto unlock; + } } while (count++ < 16); - return 0; + +unlock: + unlock_blocked_task(p, &flags); +out: + return ret; } void Index: linux-2.6/include/linux/sched.h =================================================================== --- linux-2.6.orig/include/linux/sched.h +++ linux-2.6/include/linux/sched.h @@ -1332,6 +1332,8 @@ extern void FASTCALL(wake_up_new_task(st #endif extern void FASTCALL(sched_fork(struct task_struct * p, int clone_flags)); extern void FASTCALL(sched_exit(struct task_struct * p)); +extern int lock_blocked_task(struct task_struct *p, unsigned long *flags); +extern void unlock_blocked_task(struct task_struct *p, unsigned long *flags); extern int in_group_p(gid_t); extern int in_egroup_p(gid_t); Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -1177,6 +1177,25 @@ repeat: task_rq_unlock(rq, &flags); } +int lock_blocked_task(struct task_struct *p, unsigned long *flags) +{ + struct rq *rq; + + rq = task_rq_lock(p, flags); + if (p->state == TASK_RUNNING || task_running(rq, p)) { + task_rq_unlock(rq, flags); + return 0; + } + + return 1; +} + +void unlock_blocked_task(struct task_struct *p, unsigned long *flags) +{ + task_rq_unlock(task_rq(p), flags); +} + + /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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