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Message-Id: <1306262259-7285-8-git-send-email-tj@kernel.org>
Date: Tue, 24 May 2011 20:37:27 +0200
From: Tejun Heo <tj@...nel.org>
To: oleg@...hat.com
Cc: vda.linux@...glemail.com, jan.kratochvil@...hat.com,
linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com,
pedro@...esourcery.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 07/19] ptrace: use bit_waitqueue for TRAPPING instead of wait_chldexit
ptracer->signal->wait_chldexit was used to wait for TRAPPING; however,
->wait_chldexit was already complicated with waker-side filtering
without adding TRAPPING wait on top of it. Also, it unnecessarily
made TRAPPING clearing depend on the current ptrace relationship - if
the ptracee is detached, wakeup is lost.
There is no reason to use signal->wait_chldexit here. We're just
waiting for JOBCTL_TRAPPING bit to clear and given the relatively
infrequent use of ptrace, bit_waitqueue can serve it perfectly.
This patch makes JOBCTL_TRAPPING wait use bit_waitqueue instead of
signal->wait_chldexit.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/ptrace.c | 10 ++++++++--
kernel/signal.c | 3 +--
2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index b44dc43..3be5d1b 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -25,6 +25,12 @@
#include <linux/hw_breakpoint.h>
+static int ptrace_trapping_sleep_fn(void *flags)
+{
+ schedule();
+ return 0;
+}
+
/*
* ptrace a task: make the debugger its new parent and
* move it to the ptrace list.
@@ -273,8 +279,8 @@ unlock_creds:
mutex_unlock(&task->signal->cred_guard_mutex);
out:
if (wait_trap)
- wait_event(current->signal->wait_chldexit,
- !(task->jobctl & JOBCTL_TRAPPING));
+ wait_on_bit(&task->jobctl, ilog2(JOBCTL_TRAPPING),
+ ptrace_trapping_sleep_fn, TASK_UNINTERRUPTIBLE);
return retval;
}
diff --git a/kernel/signal.c b/kernel/signal.c
index 17feedf..106b47e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -272,8 +272,7 @@ static void task_clear_jobctl_trapping(struct task_struct *task)
{
if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
task->jobctl &= ~JOBCTL_TRAPPING;
- __wake_up_sync_key(&task->parent->signal->wait_chldexit,
- TASK_UNINTERRUPTIBLE, 1, task);
+ wake_up_bit(&task->jobctl, ilog2(JOBCTL_TRAPPING));
}
}
--
1.7.1
--
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