linux-kernel - [PATCH] kretprobe events missing on 2-core KVM guest

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Message-Id: <20221025100117.18667-1-wuqiang.matt@bytedance.com>
Date:   Tue, 25 Oct 2022 18:01:17 +0800
From:   wuqiang <wuqiang.matt@...edance.com>
To:     mhiramat@...nel.org, davem@...emloft.net,
        anil.s.keshavamurthy@...el.com, naveen.n.rao@...ux.ibm.com
Cc:     linux-kernel@...r.kernel.org, mattwu@....com,
        wuqiang <wuqiang.matt@...edance.com>
Subject: [PATCH] kretprobe events missing on 2-core KVM guest

Default value of maxactive is set as num_possible_cpus() for nonpreemptable
systems. For a 2-core system, only 2 kretprobe instances would be allocated
in default, then these 2 instances for execve kretprobe are very likely to
be used up with a pipelined command.

This patch increases the minimum of maxactive to 10.

Signed-off-by: wuqiang <wuqiang.matt@...edance.com>
---
 kernel/kprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 3220b0a2fb4a..b781dee3f552 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2211,7 +2211,7 @@ int register_kretprobe(struct kretprobe *rp)
 #ifdef CONFIG_PREEMPTION
 		rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
 #else
-		rp->maxactive = num_possible_cpus();
+		rp->maxactive = max_t(unsigned int, 10, num_possible_cpus());
 #endif
 	}
 #ifdef CONFIG_KRETPROBE_ON_RETHOOK
-- 
2.34.1