From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- Documentation/driver-api/dmaengine/dmatest.rst | 232 +++++++++++++++++++++++++ 1 file changed, 232 insertions(+) create mode 100644 Documentation/driver-api/dmaengine/dmatest.rst (limited to 'Documentation/driver-api/dmaengine/dmatest.rst') diff --git a/Documentation/driver-api/dmaengine/dmatest.rst b/Documentation/driver-api/dmaengine/dmatest.rst new file mode 100644 index 000000000..e2a63cefd --- /dev/null +++ b/Documentation/driver-api/dmaengine/dmatest.rst @@ -0,0 +1,232 @@ +============== +DMA Test Guide +============== + +Andy Shevchenko + +This small document introduces how to test DMA drivers using dmatest module. + +The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using +various lengths and various offsets into the source and destination buffers. It +will initialize both buffers with a repeatable pattern and verify that the DMA +engine copies the requested region and nothing more. It will also verify that +the bytes aren't swapped around, and that the source buffer isn't modified. + +The dmatest module can be configured to test a specific channel. It can also +test multiple channels at the same time, and it can start multiple threads +competing for the same channel. + +.. note:: + The test suite works only on the channels that have at least one + capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET + (const-to-memory or memory-to-memory, when emulated), DMA_XOR, DMA_PQ. + +.. note:: + In case of any related questions use the official mailing list + dmaengine@vger.kernel.org. + +Part 1 - How to build the test module +===================================== + +The menuconfig contains an option that could be found by following path: + + Device Drivers -> DMA Engine support -> DMA Test client + +In the configuration file the option called CONFIG_DMATEST. The dmatest could +be built as module or inside kernel. Let's consider those cases. + +Part 2 - When dmatest is built as a module +========================================== + +Example of usage:: + + % modprobe dmatest timeout=2000 iterations=1 channel=dma0chan0 run=1 + +...or:: + + % modprobe dmatest + % echo 2000 > /sys/module/dmatest/parameters/timeout + % echo 1 > /sys/module/dmatest/parameters/iterations + % echo dma0chan0 > /sys/module/dmatest/parameters/channel + % echo 1 > /sys/module/dmatest/parameters/run + +...or on the kernel command line:: + + dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1 + +Example of multi-channel test usage (new in the 5.0 kernel):: + + % modprobe dmatest + % echo 2000 > /sys/module/dmatest/parameters/timeout + % echo 1 > /sys/module/dmatest/parameters/iterations + % echo dma0chan0 > /sys/module/dmatest/parameters/channel + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + % echo 1 > /sys/module/dmatest/parameters/run + +.. note:: + For all tests, starting in the 5.0 kernel, either single- or multi-channel, + the channel parameter(s) must be set after all other parameters. It is at + that time that the existing parameter values are acquired for use by the + thread(s). All other parameters are shared. Therefore, if changes are made + to any of the other parameters, and an additional channel specified, the + (shared) parameters used for all threads will use the new values. + After the channels are specified, each thread is set as pending. All threads + begin execution when the run parameter is set to 1. + +.. hint:: + A list of available channels can be found by running the following command:: + + % ls -1 /sys/class/dma/ + +Once started a message like " dmatest: Added 1 threads using dma0chan0" is +emitted. A thread for that specific channel is created and is now pending, the +pending thread is started once run is to 1. + +Note that running a new test will not stop any in progress test. + +The following command returns the state of the test. :: + + % cat /sys/module/dmatest/parameters/run + +To wait for test completion userspace can poll 'run' until it is false, or use +the wait parameter. Specifying 'wait=1' when loading the module causes module +initialization to pause until a test run has completed, while reading +/sys/module/dmatest/parameters/wait waits for any running test to complete +before returning. For example, the following scripts wait for 42 tests +to complete before exiting. Note that if 'iterations' is set to 'infinite' then +waiting is disabled. + +Example:: + + % modprobe dmatest run=1 iterations=42 wait=1 + % modprobe -r dmatest + +...or:: + + % modprobe dmatest run=1 iterations=42 + % cat /sys/module/dmatest/parameters/wait + % modprobe -r dmatest + +Part 3 - When built-in in the kernel +==================================== + +The module parameters that is supplied to the kernel command line will be used +for the first performed test. After user gets a control, the test could be +re-run with the same or different parameters. For the details see the above +section `Part 2 - When dmatest is built as a module`_. + +In both cases the module parameters are used as the actual values for the test +case. You always could check them at run-time by running :: + + % grep -H . /sys/module/dmatest/parameters/* + +Part 4 - Gathering the test results +=================================== + +Test results are printed to the kernel log buffer with the format:: + + "dmatest: result : : '' with src_off= dst_off= len= ()" + +Example of output:: + + % dmesg | tail -n 1 + dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0) + +The message format is unified across the different types of errors. A +number in the parentheses represents additional information, e.g. error +code, error counter, or status. A test thread also emits a summary line at +completion listing the number of tests executed, number that failed, and a +result code. + +Example:: + + % dmesg | tail -n 1 + dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0) + +The details of a data miscompare error are also emitted, but do not follow the +above format. + +Part 5 - Handling channel allocation +==================================== + +Allocating Channels +------------------- + +Channels do not need to be configured prior to starting a test run. Attempting +to run the test without configuring the channels will result in testing any +channels that are available. + +Example:: + + % echo 1 > /sys/module/dmatest/parameters/run + dmatest: No channels configured, continue with any + +Channels are registered using the "channel" parameter. Channels can be requested by their +name, once requested, the channel is registered and a pending thread is added to the test list. + +Example:: + + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan2 + +More channels can be added by repeating the example above. +Reading back the channel parameter will return the name of last channel that was added successfully. + +Example:: + + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan1 + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan2 + % cat /sys/module/dmatest/parameters/channel + dma0chan2 + +Another method of requesting channels is to request a channel with an empty string, Doing so +will request all channels available to be tested: + +Example:: + + % echo "" > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan0 + dmatest: Added 1 threads using dma0chan3 + dmatest: Added 1 threads using dma0chan4 + dmatest: Added 1 threads using dma0chan5 + dmatest: Added 1 threads using dma0chan6 + dmatest: Added 1 threads using dma0chan7 + dmatest: Added 1 threads using dma0chan8 + +At any point during the test configuration, reading the "test_list" parameter will +print the list of currently pending tests. + +Example:: + + % cat /sys/module/dmatest/parameters/test_list + dmatest: 1 threads using dma0chan0 + dmatest: 1 threads using dma0chan3 + dmatest: 1 threads using dma0chan4 + dmatest: 1 threads using dma0chan5 + dmatest: 1 threads using dma0chan6 + dmatest: 1 threads using dma0chan7 + dmatest: 1 threads using dma0chan8 + +Note: Channels will have to be configured for each test run as channel configurations do not +carry across to the next test run. + +Releasing Channels +------------------- + +Channels can be freed by setting run to 0. + +Example:: + + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan1 + % cat /sys/class/dma/dma0chan1/in_use + 1 + % echo 0 > /sys/module/dmatest/parameters/run + % cat /sys/class/dma/dma0chan1/in_use + 0 + +Channels allocated by previous test runs are automatically freed when a new +channel is requested after completing a successful test run. -- cgit v1.3.1