From: Masami Hiramatsu <mhiramat@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Anders Roxell <anders.roxell@linaro.org>,
paulmck@kernel.org, joel@joelfernandes.org,
"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
David Miller <davem@davemloft.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH -tip V4 1/4] kprobes: Suppress the suspicious RCU warning on kprobes
Date: Wed, 26 Feb 2020 17:59:30 +0900 [thread overview]
Message-ID: <158270757059.18966.14260537198561848568.stgit@devnote2> (raw)
In-Reply-To: <158270755997.18966.3544449431956918068.stgit@devnote2>
Anders reported that the lockdep warns that suspicious
RCU list usage in register_kprobe() (detected by
CONFIG_PROVE_RCU_LIST.) This is because get_kprobe()
access kprobe_table[] by hlist_for_each_entry_rcu()
without rcu_read_lock.
If we call get_kprobe() from the breakpoint handler context,
it is run with preempt disabled, so this is not a problem.
But in other cases, instead of rcu_read_lock(), we locks
kprobe_mutex so that the kprobe_table[] is not updated.
So, current code is safe, but still not good from the view
point of RCU.
Joel suggested that we can silent that warning by passing
lockdep_is_held() to the last argument of
hlist_for_each_entry_rcu().
Add lockdep_is_held(&kprobe_mutex) at the end of the
hlist_for_each_entry_rcu() to suppress the warning.
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Suggested-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
kernel/kprobes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2625c241ac00..bd484392d789 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -326,7 +326,8 @@ struct kprobe *get_kprobe(void *addr)
struct kprobe *p;
head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
- hlist_for_each_entry_rcu(p, head, hlist) {
+ hlist_for_each_entry_rcu(p, head, hlist,
+ lockdep_is_held(&kprobe_mutex)) {
if (p->addr == addr)
return p;
}
next prev parent reply other threads:[~2020-02-26 8:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 8:59 [PATCH -tip V4 0/4] kprobes: Fixes and cleanups Masami Hiramatsu
2020-02-26 8:59 ` Masami Hiramatsu [this message]
2020-02-26 8:59 ` [PATCH -tip V4 2/4] kprobes: Use non RCU traversal APIs on kprobe_tables if possible Masami Hiramatsu
2020-02-26 8:59 ` [PATCH -tip V4 3/4] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe_mutex Masami Hiramatsu
2020-03-03 23:52 ` Steven Rostedt
2020-03-04 7:18 ` Masami Hiramatsu
2020-02-26 9:00 ` [PATCH -tip V4 4/4] kprobes: Remove redundant arch_disarm_kprobe() call Masami Hiramatsu
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