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Subject[PREEMPT_RT] [PATCH 2/2] Use write_trylock_irqsave in ptrace_attach
Date
Hi Ingo,

This patch makes ptrace_attach() use the new API write_trylock_irqsave(). With
this, the code in ptrace_attach() will be same for mainline and -rt. On -rt,
write_trylock_irqsave() doesn't disable irqs and hence the problem is
avoided.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>

Index: linux-2.6.21-rt1_patch/kernel/ptrace.c
===================================================================
--- linux-2.6.21-rt1_patch.orig/kernel/ptrace.c 2007-05-10 11:28:57.000000000
+0530
+++ linux-2.6.21-rt1_patch/kernel/ptrace.c 2007-05-10 11:29:13.000000000 +0530
@@ -160,6 +160,7 @@
int ptrace_attach(struct task_struct *task)
{
int retval;
+ unsigned long flags;

retval = -EPERM;
if (task->pid <= 1)
@@ -178,9 +179,7 @@
* cpu's that may have task_lock).
*/
task_lock(task);
- local_irq_disable();
- if (!write_trylock(&tasklist_lock)) {
- local_irq_enable();
+ if (!write_trylock_irqsave(&tasklist_lock, flags)) {
task_unlock(task);
do {
cpu_relax();
@@ -208,7 +207,7 @@
force_sig_specific(SIGSTOP, task);

bad:
- write_unlock_irq(&tasklist_lock);
+ write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
out:
return retval;
-
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