diff options
| author | Chen, Kenneth W <kenneth.w.chen@intel.com> | 2006-01-26 18:24:59 -0800 |
|---|---|---|
| committer | Tony Luck <tony.luck@intel.com> | 2006-02-02 13:20:42 -0800 |
| commit | f8efa27662532ad5adb2790bfc3f4c78e019cfad (patch) | |
| tree | 848c4935674ed965256ef328a6b69316ebad6a8c | |
| parent | df080e7c94c8f4b8334614159fa079aaeece5670 (diff) | |
[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 <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
| -rw-r--r-- | include/asm-ia64/system.h | 25 |
1 files changed, 0 insertions, 25 deletions
diff --git a/include/asm-ia64/system.h b/include/asm-ia64/system.h index 80c5a234e25..06253871562 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) |