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-rw-r--r--kernel/ptrace.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index b0f8da8..921c22a 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -155,8 +155,26 @@ int ptrace_attach(struct task_struct *task)
if (task->tgid == current->tgid)
goto out;
- write_lock_irq(&tasklist_lock);
+repeat:
+ /*
+ * Nasty, nasty.
+ *
+ * We want to hold both the task-lock and the
+ * tasklist_lock for writing at the same time.
+ * But that's against the rules (tasklist_lock
+ * is taken for reading by interrupts on other
+ * cpu's that may have task_lock).
+ */
task_lock(task);
+ local_irq_disable();
+ if (!write_trylock(&tasklist_lock)) {
+ local_irq_enable();
+ task_unlock(task);
+ do {
+ cpu_relax();
+ } while (!write_can_lock(&tasklist_lock));
+ goto repeat;
+ }
/* the same process cannot be attached many times */
if (task->ptrace & PT_PTRACED)
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