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 --- tools/counter/counter_example.c | 92 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 tools/counter/counter_example.c (limited to 'tools/counter/counter_example.c') diff --git a/tools/counter/counter_example.c b/tools/counter/counter_example.c new file mode 100644 index 000000000..be55287b9 --- /dev/null +++ b/tools/counter/counter_example.c @@ -0,0 +1,92 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Counter - example userspace application + * + * The userspace application opens /dev/counter0, configures the + * COUNTER_EVENT_INDEX event channel 0 to gather Count 0 count and Count + * 1 count, and prints out the data as it becomes available on the + * character device node. + * + * Copyright (C) 2021 William Breathitt Gray + */ +#include +#include +#include +#include +#include +#include +#include + +static struct counter_watch watches[2] = { + { + /* Component data: Count 0 count */ + .component.type = COUNTER_COMPONENT_COUNT, + .component.scope = COUNTER_SCOPE_COUNT, + .component.parent = 0, + /* Event type: Index */ + .event = COUNTER_EVENT_INDEX, + /* Device event channel 0 */ + .channel = 0, + }, + { + /* Component data: Count 1 count */ + .component.type = COUNTER_COMPONENT_COUNT, + .component.scope = COUNTER_SCOPE_COUNT, + .component.parent = 1, + /* Event type: Index */ + .event = COUNTER_EVENT_INDEX, + /* Device event channel 0 */ + .channel = 0, + }, +}; + +int main(void) +{ + int fd; + int ret; + int i; + struct counter_event event_data[2]; + + fd = open("/dev/counter0", O_RDWR); + if (fd == -1) { + perror("Unable to open /dev/counter0"); + return 1; + } + + for (i = 0; i < 2; i++) { + ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + i); + if (ret == -1) { + fprintf(stderr, "Error adding watches[%d]: %s\n", i, + strerror(errno)); + return 1; + } + } + ret = ioctl(fd, COUNTER_ENABLE_EVENTS_IOCTL); + if (ret == -1) { + perror("Error enabling events"); + return 1; + } + + for (;;) { + ret = read(fd, event_data, sizeof(event_data)); + if (ret == -1) { + perror("Failed to read event data"); + return 1; + } + + if (ret != sizeof(event_data)) { + fprintf(stderr, "Failed to read event data\n"); + return -EIO; + } + + printf("Timestamp 0: %llu\tCount 0: %llu\n" + "Error Message 0: %s\n" + "Timestamp 1: %llu\tCount 1: %llu\n" + "Error Message 1: %s\n", + event_data[0].timestamp, event_data[0].value, + strerror(event_data[0].status), + event_data[1].timestamp, event_data[1].value, + strerror(event_data[1].status)); + } + + return 0; +} -- cgit v1.3.1