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e4b42053b7
- Fix adding a new fgraph callback after function graph tracing has already started. If the new caller does not initialize its hash before registering the fgraph_ops, it can cause a NULL pointer dereference. Fix this by adding a new parameter to ftrace_graph_enable_direct() passing in the newly added gops directly and not rely on using the fgraph_array[], as entries in the fgraph_array[] must be initialized. Assign the new gops to the fgraph_array[] after it goes through ftrace_startup_subops() as that will properly initialize the gops->ops and initialize its hashes. - Fix a memory leak in fgraph storage memory test. If the "multiple fgraph storage on a function" boot up selftest fails in the registering of the function graph tracer, it will not free the memory it allocated for the filter. Break the loop up into two where it allocates the filters first and then registers the functions where any errors will do the appropriate clean ups. - Only clear the timerlat timers if it has an associated kthread. In the rtla tool that uses timerlat, if it was killed just as it was shutting down, the signals can free the kthread and the timer. But the closing of the timerlat files could cause the hrtimer_cancel() to be called on the already freed timer. As the kthread variable is is set to NULL when the kthreads are stopped and the timers are freed it can be used to know not to call hrtimer_cancel() on the timer if the kthread variable is NULL. - Use a cpumask to keep track of osnoise/timerlat kthreads The timerlat tracer can use user space threads for its analysis. With the killing of the rtla tool, the kernel can get confused between if it is using a user space thread to analyze or one of its own kernel threads. When this confusion happens, kthread_stop() can be called on a user space thread and bad things happen. As the kernel threads are per-cpu, a bitmask can be used to know when a kernel thread is used or when a user space thread is used. - Add missing interface_lock to osnoise/timerlat stop_kthread() The stop_kthread() function in osnoise/timerlat clears the osnoise kthread variable, and if it was a user space thread does a put_task on it. But this can race with the closing of the timerlat files that also does a put_task on the kthread, and if the race happens the task will have put_task called on it twice and oops. - Add cond_resched() to the tracing_iter_reset() loop. The latency tracers keep writing to the ring buffer without resetting when it issues a new "start" event (like interrupts being disabled). When reading the buffer with an iterator, the tracing_iter_reset() sets its pointer to that start event by walking through all the events in the buffer until it gets to the time stamp of the start event. In the case of a very large buffer, the loop that looks for the start event has been reported taking a very long time with a non preempt kernel that it can trigger a soft lock up warning. Add a cond_resched() into that loop to make sure that doesn't happen. - Use list_del_rcu() for eventfs ei->list variable It was reported that running loops of creating and deleting kprobe events could cause a crash due to the eventfs list iteration hitting a LIST_POISON variable. This is because the list is protected by SRCU but when an item is deleted from the list, it was using list_del() which poisons the "next" pointer. This is what list_del_rcu() was to prevent. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZtohNBQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qtoNAQDQKjomYLCpLz2EqgHZ6VB81QVrHuqt cU7xuEfUJDzyyAEA/n0t6quIdjYRd6R2/KxGkP6By/805Coq4IZMTgNQmw0= =nZ7k -----END PGP SIGNATURE----- Merge tag 'trace-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix adding a new fgraph callback after function graph tracing has already started. If the new caller does not initialize its hash before registering the fgraph_ops, it can cause a NULL pointer dereference. Fix this by adding a new parameter to ftrace_graph_enable_direct() passing in the newly added gops directly and not rely on using the fgraph_array[], as entries in the fgraph_array[] must be initialized. Assign the new gops to the fgraph_array[] after it goes through ftrace_startup_subops() as that will properly initialize the gops->ops and initialize its hashes. - Fix a memory leak in fgraph storage memory test. If the "multiple fgraph storage on a function" boot up selftest fails in the registering of the function graph tracer, it will not free the memory it allocated for the filter. Break the loop up into two where it allocates the filters first and then registers the functions where any errors will do the appropriate clean ups. - Only clear the timerlat timers if it has an associated kthread. In the rtla tool that uses timerlat, if it was killed just as it was shutting down, the signals can free the kthread and the timer. But the closing of the timerlat files could cause the hrtimer_cancel() to be called on the already freed timer. As the kthread variable is is set to NULL when the kthreads are stopped and the timers are freed it can be used to know not to call hrtimer_cancel() on the timer if the kthread variable is NULL. - Use a cpumask to keep track of osnoise/timerlat kthreads The timerlat tracer can use user space threads for its analysis. With the killing of the rtla tool, the kernel can get confused between if it is using a user space thread to analyze or one of its own kernel threads. When this confusion happens, kthread_stop() can be called on a user space thread and bad things happen. As the kernel threads are per-cpu, a bitmask can be used to know when a kernel thread is used or when a user space thread is used. - Add missing interface_lock to osnoise/timerlat stop_kthread() The stop_kthread() function in osnoise/timerlat clears the osnoise kthread variable, and if it was a user space thread does a put_task on it. But this can race with the closing of the timerlat files that also does a put_task on the kthread, and if the race happens the task will have put_task called on it twice and oops. - Add cond_resched() to the tracing_iter_reset() loop. The latency tracers keep writing to the ring buffer without resetting when it issues a new "start" event (like interrupts being disabled). When reading the buffer with an iterator, the tracing_iter_reset() sets its pointer to that start event by walking through all the events in the buffer until it gets to the time stamp of the start event. In the case of a very large buffer, the loop that looks for the start event has been reported taking a very long time with a non preempt kernel that it can trigger a soft lock up warning. Add a cond_resched() into that loop to make sure that doesn't happen. - Use list_del_rcu() for eventfs ei->list variable It was reported that running loops of creating and deleting kprobe events could cause a crash due to the eventfs list iteration hitting a LIST_POISON variable. This is because the list is protected by SRCU but when an item is deleted from the list, it was using list_del() which poisons the "next" pointer. This is what list_del_rcu() was to prevent. * tag 'trace-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread() tracing/timerlat: Only clear timer if a kthread exists tracing/osnoise: Use a cpumask to know what threads are kthreads eventfs: Use list_del_rcu() for SRCU protected list variable tracing: Avoid possible softlockup in tracing_iter_reset() tracing: Fix memory leak in fgraph storage selftest tracing: fgraph: Fix to add new fgraph_ops to array after ftrace_startup_subops() |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.