ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 229 insertions, 0 deletions

diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
new file mode 100644
index 000000000..65444ff14
--- /dev/null
+++ b/net/ipv4/tcp_bic.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Binary Increase Congestion control for TCP
+ * Home page:
+ *      http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC
+ * This is from the implementation of BICTCP in
+ * Lison-Xu, Kahaled Harfoush, and Injong Rhee.
+ *  "Binary Increase Congestion Control for Fast, Long Distance
+ *  Networks" in InfoComm 2004
+ * Available from:
+ *  http://netsrv.csc.ncsu.edu/export/bitcp.pdf
+ *
+ * Unless BIC is enabled and congestion window is large
+ * this behaves the same as the original Reno.
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+
+#define BICTCP_BETA_SCALE    1024	/* Scale factor beta calculation
+					 * max_cwnd = snd_cwnd * beta
+					 */
+#define BICTCP_B		4	 /*
+					  * In binary search,
+					  * go to point (max+min)/N
+					  */
+
+static int fast_convergence = 1;
+static int max_increment = 16;
+static int low_window = 14;
+static int beta = 819;		/* = 819/1024 (BICTCP_BETA_SCALE) */
+static int initial_ssthresh;
+static int smooth_part = 20;
+
+module_param(fast_convergence, int, 0644);
+MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
+module_param(max_increment, int, 0644);
+MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
+module_param(low_window, int, 0644);
+MODULE_PARM_DESC(low_window, "lower bound on congestion window (for TCP friendliness)");
+module_param(beta, int, 0644);
+MODULE_PARM_DESC(beta, "beta for multiplicative increase");
+module_param(initial_ssthresh, int, 0644);
+MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
+module_param(smooth_part, int, 0644);
+MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wmax-B to Wmax");
+
+/* BIC TCP Parameters */
+struct bictcp {
+	u32	cnt;		/* increase cwnd by 1 after ACKs */
+	u32	last_max_cwnd;	/* last maximum snd_cwnd */
+	u32	last_cwnd;	/* the last snd_cwnd */
+	u32	last_time;	/* time when updated last_cwnd */
+	u32	epoch_start;	/* beginning of an epoch */
+#define ACK_RATIO_SHIFT	4
+	u32	delayed_ack;	/* estimate the ratio of Packets/ACKs << 4 */
+};
+
+static inline void bictcp_reset(struct bictcp *ca)
+{
+	ca->cnt = 0;
+	ca->last_max_cwnd = 0;
+	ca->last_cwnd = 0;
+	ca->last_time = 0;
+	ca->epoch_start = 0;
+	ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
+}
+
+static void bictcp_init(struct sock *sk)
+{
+	struct bictcp *ca = inet_csk_ca(sk);
+
+	bictcp_reset(ca);
+
+	if (initial_ssthresh)
+		WRITE_ONCE(tcp_sk(sk)->snd_ssthresh, initial_ssthresh);
+}
+
+/*
+ * Compute congestion window to use.
+ */
+static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
+{
+	if (ca->last_cwnd == cwnd &&
+	    (s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32)
+		return;
+
+	ca->last_cwnd = cwnd;
+	ca->last_time = tcp_jiffies32;
+
+	if (ca->epoch_start == 0) /* record the beginning of an epoch */
+		ca->epoch_start = tcp_jiffies32;
+
+	/* start off normal */
+	if (cwnd <= low_window) {
+		ca->cnt = cwnd;
+		return;
+	}
+
+	/* binary increase */
+	if (cwnd < ca->last_max_cwnd) {
+		__u32	dist = (ca->last_max_cwnd - cwnd)
+			/ BICTCP_B;
+
+		if (dist > max_increment)
+			/* linear increase */
+			ca->cnt = cwnd / max_increment;
+		else if (dist <= 1U)
+			/* binary search increase */
+			ca->cnt = (cwnd * smooth_part) / BICTCP_B;
+		else
+			/* binary search increase */
+			ca->cnt = cwnd / dist;
+	} else {
+		/* slow start AMD linear increase */
+		if (cwnd < ca->last_max_cwnd + BICTCP_B)
+			/* slow start */
+			ca->cnt = (cwnd * smooth_part) / BICTCP_B;
+		else if (cwnd < ca->last_max_cwnd + max_increment*(BICTCP_B-1))
+			/* slow start */
+			ca->cnt = (cwnd * (BICTCP_B-1))
+				/ (cwnd - ca->last_max_cwnd);
+		else
+			/* linear increase */
+			ca->cnt = cwnd / max_increment;
+	}
+
+	/* if in slow start or link utilization is very low */
+	if (ca->last_max_cwnd == 0) {
+		if (ca->cnt > 20) /* increase cwnd 5% per RTT */
+			ca->cnt = 20;
+	}
+
+	ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack;
+	if (ca->cnt == 0)			/* cannot be zero */
+		ca->cnt = 1;
+}
+
+static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct bictcp *ca = inet_csk_ca(sk);
+
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	if (tcp_in_slow_start(tp)) {
+		acked = tcp_slow_start(tp, acked);
+		if (!acked)
+			return;
+	}
+	bictcp_update(ca, tcp_snd_cwnd(tp));
+	tcp_cong_avoid_ai(tp, ca->cnt, acked);
+}
+
+/*
+ *	behave like Reno until low_window is reached,
+ *	then increase congestion window slowly
+ */
+static u32 bictcp_recalc_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct bictcp *ca = inet_csk_ca(sk);
+
+	ca->epoch_start = 0;	/* end of epoch */
+
+	/* Wmax and fast convergence */
+	if (tcp_snd_cwnd(tp) < ca->last_max_cwnd && fast_convergence)
+		ca->last_max_cwnd = (tcp_snd_cwnd(tp) * (BICTCP_BETA_SCALE + beta))
+			/ (2 * BICTCP_BETA_SCALE);
+	else
+		ca->last_max_cwnd = tcp_snd_cwnd(tp);
+
+	if (tcp_snd_cwnd(tp) <= low_window)
+		return max(tcp_snd_cwnd(tp) >> 1U, 2U);
+	else
+		return max((tcp_snd_cwnd(tp) * beta) / BICTCP_BETA_SCALE, 2U);
+}
+
+static void bictcp_state(struct sock *sk, u8 new_state)
+{
+	if (new_state == TCP_CA_Loss)
+		bictcp_reset(inet_csk_ca(sk));
+}
+
+/* Track delayed acknowledgment ratio using sliding window
+ * ratio = (15*ratio + sample) / 16
+ */
+static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (icsk->icsk_ca_state == TCP_CA_Open) {
+		struct bictcp *ca = inet_csk_ca(sk);
+
+		ca->delayed_ack += sample->pkts_acked -
+			(ca->delayed_ack >> ACK_RATIO_SHIFT);
+	}
+}
+
+static struct tcp_congestion_ops bictcp __read_mostly = {
+	.init		= bictcp_init,
+	.ssthresh	= bictcp_recalc_ssthresh,
+	.cong_avoid	= bictcp_cong_avoid,
+	.set_state	= bictcp_state,
+	.undo_cwnd	= tcp_reno_undo_cwnd,
+	.pkts_acked     = bictcp_acked,
+	.owner		= THIS_MODULE,
+	.name		= "bic",
+};
+
+static int __init bictcp_register(void)
+{
+	BUILD_BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE);
+	return tcp_register_congestion_control(&bictcp);
+}
+
+static void __exit bictcp_unregister(void)
+{
+	tcp_unregister_congestion_control(&bictcp);
+}
+
+module_init(bictcp_register);
+module_exit(bictcp_unregister);
+
+MODULE_AUTHOR("Stephen Hemminger");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("BIC TCP");