kernel/linux.git/tools/tracing/rtla/src/trace.c, branch v7.1-rc5

rtla/trace: Fix I/O handling in save_trace_to_file()

2026-03-11T14:29:50+00:00

The read/write loop in save_trace_to_file() does not correctly handle errors from the read() and write() system calls. If either call is interrupted by a signal, it returns -1 with errno set to EINTR, but the code treats this as a fatal error and aborts the save operation. Additionally, write() may perform a partial write, returning fewer bytes than requested, which the code does not handle. Fix the I/O loop by introducing proper error handling. The return value of read() is now stored in a ssize_t variable and checked for errors, with EINTR causing a retry. For write(), an inner loop ensures all bytes are written, handling both EINTR and partial writes. Error messages now include strerror() output for better debugging. This follows the same pattern established in the previous commit that fixed trace_event_save_hist(), ensuring consistent and robust I/O handling throughout the trace saving code. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-17-wander@redhat.com Signed-off-by: Tomas Glozar

rtla/trace: Fix write loop in trace_event_save_hist()

2026-03-11T14:29:50+00:00

The write loop in trace_event_save_hist() does not correctly handle errors from the write() system call. If write() returns -1, this value is added to the loop index, leading to an incorrect memory access on the next iteration and potentially an infinite loop. The loop also fails to handle EINTR. Fix the write loop by introducing proper error handling. The return value of write() is now stored in a ssize_t variable and checked for errors. The loop retries the call if interrupted by a signal and breaks on any other error after logging it with strerror(). Additionally, change the index variable type from int to size_t to match the type used for buffer sizes and by strlen(), improving type safety. Fixes: 761916fd02c2 ("rtla/trace: Save event histogram output to a file") Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-16-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Use str_has_prefix() for prefix checks

2026-03-11T14:29:50+00:00

The code currently uses strncmp() combined with strlen() to check if a string starts with a specific prefix. This pattern is verbose and prone to errors if the length does not match the prefix string. Replace this pattern with the str_has_prefix() helper function in both trace.c and utils.c. This improves code readability and safety by handling the prefix length calculation automatically. In addition, remove the unused retval variable from trace_event_save_hist() in trace.c to clean up the function and silence potential compiler warnings. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-12-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Simplify code by caching string lengths

2026-03-10T09:32:37+00:00

Simplify trace_event_save_hist() and set_comm_cgroup() by computing string lengths once and storing them in local variables, rather than calling strlen() multiple times on the same unchanged strings. This makes the code clearer by eliminating redundant function calls and improving readability. In trace_event_save_hist(), the write loop previously called strlen() on the hist buffer twice per iteration for both the size calculation and loop condition. Store the length in hist_len before entering the loop. In set_comm_cgroup(), strlen() was called on cgroup_path up to three times in succession. Store the result in cg_path_len to use in both the offset calculation and size parameter for subsequent append operations. This simplification makes the code easier to read and maintain without changing program behavior. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-7-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Replace magic number with MAX_PATH

2026-03-10T09:32:37+00:00

The trace functions use a buffer to manipulate strings that will be written to tracefs files. These buffers are defined with a magic number of 1024, which is a common source of vulnerabilities. Replace the magic number 1024 with the MAX_PATH macro to make the code safer and more readable. While at it, replace other instances of the magic number with ARRAY_SIZE() when the buffer is locally defined. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-6-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Exit on memory allocation failures during initialization

2026-03-10T09:32:37+00:00

Most memory allocations in rtla happen during early initialization before any resources are acquired that would require cleanup. In these cases, propagating allocation errors just adds complexity without any benefit. There's nothing to clean up, and the program must exit anyway. This patch introduces fatal allocation wrappers (calloc_fatal, reallocarray_fatal, strdup_fatal) that call fatal() on allocation failure. These wrappers simplify the code by eliminating unnecessary error propagation paths. The patch converts early allocations to use these wrappers in actions_init() and related action functions, osnoise_context_alloc() and osnoise_init_tool(), trace_instance_init() and trace event functions, and parameter structure allocations in main functions. This simplifies the code while maintaining the same behavior: immediate exit on allocation failure during initialization. Allocations that require cleanup, such as those in histogram allocation functions with goto cleanup paths, are left unchanged and continue to return errors. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-2-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Remove unused headers

2026-01-07T14:57:55+00:00

Remove unused includes for and to clean up the code and reduce unnecessary dependencies. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260106133655.249887-12-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Fix segfault in save_trace_to_file call

2025-03-26T14:35:20+00:00

Running rtla with exit on threshold, but without saving trace leads to a segmenetation fault: $ rtla timerlat hist -T 10 ... Max timerlat IRQ latency from idle: 4.29 us in cpu 0 Segmentation fault This is caused by null pointer deference in the call of save_trace_to_file, which attempts to dereference an uninitialized osnoise_tool variable: save_trace_to_file(record->trace.inst, params->trace_output); ^ this is uninitialized if params->trace_output is not set Fix this by not attempting to dereference "record" if it is NULL and passing NULL instead. As a safety measure, the first field is also checked for NULL inside save_trace_to_file. Cc: John Kacur Cc: Luis Goncalves Cc: Costa Shulyupin Link: https://lore.kernel.org/20250313141034.299117-1-tglozar@redhat.com Fixes: dc4d4e7c72d1 ("rtla: Refactor save_trace_to_file") Signed-off-by: Tomas Glozar Signed-off-by: Steven Rostedt (Google)

rtla: Refactor save_trace_to_file

2025-03-04T19:17:19+00:00

The functions osnoise_hist_main(), osnoise_top_main(), timerlat_hist_main(), and timerlat_top_main() are lengthy and contain duplicated code. Refactor by consolidating the duplicate lines into the save_trace_to_file() function. Cc: Daniel Bristot de Oliveira Cc: John Kacur Cc: "Luis Claudio R. Goncalves" Cc: Eder Zulian Cc: Dan Carpenter Cc: Gabriele Monaco Link: https://lore.kernel.org/20250219115138.406075-1-costa.shul@redhat.com Signed-off-by: Costa Shulyupin Reviewed-by: Tomas Glozar Tested-by: Tomas Glozar Signed-off-by: Steven Rostedt (Google)

rtla: Count all processed events

2025-01-24T18:46:24+00:00

Add a field processed_events to struct trace_instance and increment it in collect_registered_events, regardless of whether a handler is registered for the event. The purpose is to calculate the percentage of events that were missed due to tracefs buffer overflow. Cc: John Kacur Cc: Luis Goncalves Cc: Gabriele Monaco Link: https://lore.kernel.org/20250123142339.990300-3-tglozar@redhat.com Signed-off-by: Tomas Glozar Signed-off-by: Steven Rostedt (Google)