From: Chen, Kenneth W Date: Fri, 27 Jan 2006 02:24:59 +0000 (-0800) Subject: [IA64] remove staled comments in asm/system.h X-Git-Tag: v2.6.16-rc3~141^2~10 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8efa27662532ad5adb2790bfc3f4c78e019cfad;p=linux-2.6 [IA64] remove staled comments in asm/system.h With the recent optimization made to wrap_mmu_context function, we don't hold tasklist_lock anymore when wrapping context id. The comments in asm/system.h must fall through the crack earlier. Remove staled comments. I believe it is still beneficial to unlock the runqueue lock across context switch. So leave __ARCH_WANT_UNLOCKED_CTXSW on. Signed-off-by: Ken Chen Signed-off-by: Tony Luck --- diff --git a/include/asm-ia64/system.h b/include/asm-ia64/system.h index 80c5a234e2..0625387156 100644 --- a/include/asm-ia64/system.h +++ b/include/asm-ia64/system.h @@ -249,32 +249,7 @@ extern void ia64_load_extra (struct task_struct *task); # define switch_to(prev,next,last) __switch_to(prev, next, last) #endif -/* - * On IA-64, we don't want to hold the runqueue's lock during the low-level context-switch, - * because that could cause a deadlock. Here is an example by Erich Focht: - * - * Example: - * CPU#0: - * schedule() - * -> spin_lock_irq(&rq->lock) - * -> context_switch() - * -> wrap_mmu_context() - * -> read_lock(&tasklist_lock) - * - * CPU#1: - * sys_wait4() or release_task() or forget_original_parent() - * -> write_lock(&tasklist_lock) - * -> do_notify_parent() - * -> wake_up_parent() - * -> try_to_wake_up() - * -> spin_lock_irq(&parent_rq->lock) - * - * If the parent's rq happens to be on CPU#0, we'll wait for the rq->lock - * of that CPU which will not be released, because there we wait for the - * tasklist_lock to become available. - */ #define __ARCH_WANT_UNLOCKED_CTXSW - #define ARCH_HAS_PREFETCH_SWITCH_STACK #define ia64_platform_is(x) (strcmp(x, platform_name) == 0)