Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH rcu 04/10] rcu: Make tiny RCU support leak callbacks for debug-object errors | Date | Wed, 31 Aug 2022 11:07:59 -0700 |
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From: Zqiang <qiang1.zhang@intel.com>
Currently, only Tree RCU leaks callbacks setting when it detects a duplicate call_rcu(). This commit causes Tiny RCU to also leak callbacks in this situation.
Because this is Tiny RCU, kernel size is important:
1. CONFIG_TINY_RCU=y and CONFIG_DEBUG_OBJECTS_RCU_HEAD=n (Production kernel)
Original: text data bss dec hex filename 26290663 20159823 15212544 61663030 3ace736 vmlinux
With this commit: text data bss dec hex filename 26290663 20159823 15212544 61663030 3ace736 vmlinux
2. CONFIG_TINY_RCU=y and CONFIG_DEBUG_OBJECTS_RCU_HEAD=y (Debugging kernel)
Original: text data bss dec hex filename 26291319 20160143 15212544 61664006 3aceb06 vmlinux
With this commit: text data bss dec hex filename 26291319 20160431 15212544 61664294 3acec26 vmlinux
These results show that the kernel size is unchanged for production kernels, as desired.
Signed-off-by: Zqiang <qiang1.zhang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- kernel/rcu/tiny.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index f0561ee16b9c2..943d431b908f6 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -158,6 +158,10 @@ void synchronize_rcu(void) } EXPORT_SYMBOL_GPL(synchronize_rcu); +static void tiny_rcu_leak_callback(struct rcu_head *rhp) +{ +} + /* * Post an RCU callback to be invoked after the end of an RCU grace * period. But since we have but one CPU, that would be after any @@ -165,9 +169,20 @@ EXPORT_SYMBOL_GPL(synchronize_rcu); */ void call_rcu(struct rcu_head *head, rcu_callback_t func) { + static atomic_t doublefrees; unsigned long flags; - debug_rcu_head_queue(head); + if (debug_rcu_head_queue(head)) { + if (atomic_inc_return(&doublefrees) < 4) { + pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func); + mem_dump_obj(head); + } + + if (!__is_kvfree_rcu_offset((unsigned long)head->func)) + WRITE_ONCE(head->func, tiny_rcu_leak_callback); + return; + } + head->func = func; head->next = NULL; -- 2.31.1.189.g2e36527f23
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