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authorRoland McGrath <roland@redhat.com>2008-07-25 19:45:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-26 12:00:08 -0700
commitdae33574dcf5211e1f43c7e45fa29f73ba3e00cb (patch)
tree090eb4af17451836fb39cebf57fbee64a6bd23b5 /include
parentdaded34be96b1975ff8539ff62ad8b158ce7d842 (diff)
downloadop-kernel-dev-dae33574dcf5211e1f43c7e45fa29f73ba3e00cb.zip
op-kernel-dev-dae33574dcf5211e1f43c7e45fa29f73ba3e00cb.tar.gz
tracehook: release_task
This moves the ptrace-related logic from release_task into tracehook.h and ptrace.h inlines. It provides clean hooks both before and after locking tasklist_lock, for future tracing logic to do more cleanup without the lock. This also changes release_task() itself in the rare "zap_leader" case to set the leader to EXIT_DEAD before iterating. This maintains the invariant that release_task() only ever handles a task in EXIT_DEAD. This is a common-sense invariant that is already always true except in this one arcane case of zombie leader whose parent ignores SIGCHLD. This change is harmless and only costs one store in this one rare case. It keeps the expected state more consisently sane, which is nicer when debugging weirdness in release_task(). It also lets some future code in the tracehook entry points rely on this invariant for bookkeeping. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Reviewed-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/ptrace.h13
-rw-r--r--include/linux/tracehook.h28
2 files changed, 41 insertions, 0 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index dae6d85..ed69c03 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -176,6 +176,19 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
}
}
+/**
+ * ptrace_release_task - final ptrace-related cleanup of a zombie being reaped
+ * @task: task in %EXIT_DEAD state
+ *
+ * Called with write_lock(&tasklist_lock) held.
+ */
+static inline void ptrace_release_task(struct task_struct *task)
+{
+ BUG_ON(!list_empty(&task->ptraced));
+ ptrace_unlink(task);
+ BUG_ON(!list_empty(&task->ptrace_entry));
+}
+
#ifndef force_successful_syscall_return
/*
* System call handlers that, upon successful completion, need to return a
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 830e6e1..9a5b3be 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -228,4 +228,32 @@ static inline void tracehook_report_vfork_done(struct task_struct *child,
ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid);
}
+/**
+ * tracehook_prepare_release_task - task is being reaped, clean up tracing
+ * @task: task in %EXIT_DEAD state
+ *
+ * This is called in release_task() just before @task gets finally reaped
+ * and freed. This would be the ideal place to remove and clean up any
+ * tracing-related state for @task.
+ *
+ * Called with no locks held.
+ */
+static inline void tracehook_prepare_release_task(struct task_struct *task)
+{
+}
+
+/**
+ * tracehook_finish_release_task - task is being reaped, clean up tracing
+ * @task: task in %EXIT_DEAD state
+ *
+ * This is called in release_task() when @task is being in the middle of
+ * being reaped. After this, there must be no tracing entanglements.
+ *
+ * Called with write_lock_irq(&tasklist_lock) held.
+ */
+static inline void tracehook_finish_release_task(struct task_struct *task)
+{
+ ptrace_release_task(task);
+}
+
#endif /* <linux/tracehook.h> */
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