From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/rtc/rtc-sun4v.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 drivers/rtc/rtc-sun4v.c (limited to 'drivers/rtc/rtc-sun4v.c') diff --git a/drivers/rtc/rtc-sun4v.c b/drivers/rtc/rtc-sun4v.c new file mode 100644 index 000000000..a86e27de8 --- /dev/null +++ b/drivers/rtc/rtc-sun4v.c @@ -0,0 +1,98 @@ +// SPDX-License-Identifier: GPL-2.0 +/* rtc-sun4v.c: Hypervisor based RTC for SUN4V systems. + * + * Author: David S. Miller + * + * Copyright (C) 2008 David S. Miller + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include + +#include + +static unsigned long hypervisor_get_time(void) +{ + unsigned long ret, time; + int retries = 10000; + +retry: + ret = sun4v_tod_get(&time); + if (ret == HV_EOK) + return time; + if (ret == HV_EWOULDBLOCK) { + if (--retries > 0) { + udelay(100); + goto retry; + } + pr_warn("tod_get() timed out.\n"); + return 0; + } + pr_warn("tod_get() not supported.\n"); + return 0; +} + +static int sun4v_read_time(struct device *dev, struct rtc_time *tm) +{ + rtc_time64_to_tm(hypervisor_get_time(), tm); + return 0; +} + +static int hypervisor_set_time(unsigned long secs) +{ + unsigned long ret; + int retries = 10000; + +retry: + ret = sun4v_tod_set(secs); + if (ret == HV_EOK) + return 0; + if (ret == HV_EWOULDBLOCK) { + if (--retries > 0) { + udelay(100); + goto retry; + } + pr_warn("tod_set() timed out.\n"); + return -EAGAIN; + } + pr_warn("tod_set() not supported.\n"); + return -EOPNOTSUPP; +} + +static int sun4v_set_time(struct device *dev, struct rtc_time *tm) +{ + return hypervisor_set_time(rtc_tm_to_time64(tm)); +} + +static const struct rtc_class_ops sun4v_rtc_ops = { + .read_time = sun4v_read_time, + .set_time = sun4v_set_time, +}; + +static int __init sun4v_rtc_probe(struct platform_device *pdev) +{ + struct rtc_device *rtc; + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &sun4v_rtc_ops; + rtc->range_max = U64_MAX; + platform_set_drvdata(pdev, rtc); + + return devm_rtc_register_device(rtc); +} + +static struct platform_driver sun4v_rtc_driver = { + .driver = { + .name = "rtc-sun4v", + }, +}; + +builtin_platform_driver_probe(sun4v_rtc_driver, sun4v_rtc_probe); -- cgit v1.3.1