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/xen/cpu_hotplug.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 121 insertions(+) create mode 100644 drivers/xen/cpu_hotplug.c (limited to 'drivers/xen/cpu_hotplug.c') diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c new file mode 100644 index 000000000..b96b11e2b --- /dev/null +++ b/drivers/xen/cpu_hotplug.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt + +#include + +#include +#include + +#include +#include + +static void enable_hotplug_cpu(int cpu) +{ + if (!cpu_present(cpu)) + xen_arch_register_cpu(cpu); + + set_cpu_present(cpu, true); +} + +static void disable_hotplug_cpu(int cpu) +{ + if (!cpu_is_hotpluggable(cpu)) + return; + lock_device_hotplug(); + if (cpu_online(cpu)) + device_offline(get_cpu_device(cpu)); + if (!cpu_online(cpu) && cpu_present(cpu)) { + xen_arch_unregister_cpu(cpu); + set_cpu_present(cpu, false); + } + unlock_device_hotplug(); +} + +static int vcpu_online(unsigned int cpu) +{ + int err; + char dir[16], state[16]; + + sprintf(dir, "cpu/%u", cpu); + err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state); + if (err != 1) { + if (!xen_initial_domain()) + pr_err("Unable to read cpu state\n"); + return err; + } + + if (strcmp(state, "online") == 0) + return 1; + else if (strcmp(state, "offline") == 0) + return 0; + + pr_err("unknown state(%s) on CPU%d\n", state, cpu); + return -EINVAL; +} +static void vcpu_hotplug(unsigned int cpu) +{ + if (cpu >= nr_cpu_ids || !cpu_possible(cpu)) + return; + + switch (vcpu_online(cpu)) { + case 1: + enable_hotplug_cpu(cpu); + break; + case 0: + disable_hotplug_cpu(cpu); + break; + default: + break; + } +} + +static void handle_vcpu_hotplug_event(struct xenbus_watch *watch, + const char *path, const char *token) +{ + unsigned int cpu; + char *cpustr; + + cpustr = strstr(path, "cpu/"); + if (cpustr != NULL) { + sscanf(cpustr, "cpu/%u", &cpu); + vcpu_hotplug(cpu); + } +} + +static int setup_cpu_watcher(struct notifier_block *notifier, + unsigned long event, void *data) +{ + int cpu; + static struct xenbus_watch cpu_watch = { + .node = "cpu", + .callback = handle_vcpu_hotplug_event}; + + (void)register_xenbus_watch(&cpu_watch); + + for_each_possible_cpu(cpu) { + if (vcpu_online(cpu) == 0) + disable_hotplug_cpu(cpu); + } + + return NOTIFY_DONE; +} + +static int __init setup_vcpu_hotplug_event(void) +{ + static struct notifier_block xsn_cpu = { + .notifier_call = setup_cpu_watcher }; + +#ifdef CONFIG_X86 + if (!xen_pv_domain() && !xen_pvh_domain()) +#else + if (!xen_domain()) +#endif + return -ENODEV; + + register_xenstore_notifier(&xsn_cpu); + + return 0; +} + +late_initcall(setup_vcpu_hotplug_event); + -- cgit v1.3.1