user/sven/linux.git/kernel/trace/trace_events_hist.c, branch next/HEAD

tracing: Fix fully-qualified variable reference printing in histograms

2026-04-14T09:28:10Z

The syntax for fully-qualified variable references in histograms is subsys.event.$var, which is parsed correctly, but not displayed correctly when printing a histogram spec. The current code puts the $ reference at the beginning of the fully-qualified variable name i.e. $subsys.event.var, which is incorrect. Before: trigger info: hist:keys=next_comm:vals=hitcount:wakeup_lat=common_timestamp.usecs-$sched.sched_wakeup.ts0: ... After: trigger info: hist:keys=next_comm:vals=hitcount:wakeup_lat=common_timestamp.usecs-sched.sched_wakeup.$ts0: ... Link: https://patch.msgid.link/5dee9a86d062a4dd68c2214f3d90ac93811e1951.1776112478.git.zanussi@kernel.org Signed-off-by: Tom Zanussi Signed-off-by: Steven Rostedt (Google)

tracing: Rebuild full_name on each hist_field_name() call

2026-04-14T08:59:33Z

hist_field_name() uses a static MAX_FILTER_STR_VAL buffer for fully qualified variable-reference names, but it currently appends into that buffer with strcat() without rebuilding it first. As a result, repeated calls append a new "system.event.field" name onto the previous one, which can eventually run past the end of full_name. Build the name with snprintf() on each call and return NULL if the fully qualified name does not fit in MAX_FILTER_STR_VAL. Link: https://patch.msgid.link/20260401112224.85582-1-pengpeng@iscas.ac.cn Fixes: 067fe038e70f ("tracing: Add variable reference handling to hist triggers") Reviewed-by: Tom Zanussi Tested-by: Tom Zanussi Signed-off-by: Pengpeng Hou Signed-off-by: Steven Rostedt (Google)

tracing: Free up file->private_data for use by individual events

2026-03-24T00:16:46Z

The tracing_open_file_tr() function currently copies the trace_event_file pointer from inode->i_private to file->private_data when the file is successfully opened. This duplication is not particularly useful, as all event code should utilize event_file_file() or event_file_data() to retrieve a trace_event_file pointer from a file struct and these access functions read file->f_inode->i_private. Moreover, this setup requires the code for opening hist files to explicitly clear file->private_data before calling single_open(), since this function expects the private_data member to be set to NULL and uses it to store a pointer to a seq_file. Remove the unnecessary setting of file->private_data in tracing_open_file_tr() and simplify the hist code. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Tom Zanussi Link: https://patch.msgid.link/20260219162737.314231-6-petr.pavlu@suse.com Signed-off-by: Petr Pavlu Signed-off-by: Steven Rostedt (Google)

Convert more 'alloc_obj' cases to default GFP_KERNEL arguments

2026-02-22T04:03:00Z

This converts some of the visually simpler cases that have been split over multiple lines. I only did the ones that are easy to verify the resulting diff by having just that final GFP_KERNEL argument on the next line. Somebody should probably do a proper coccinelle script for this, but for me the trivial script actually resulted in an assertion failure in the middle of the script. I probably had made it a bit _too_ trivial. So after fighting that far a while I decided to just do some of the syntactically simpler cases with variations of the previous 'sed' scripts. The more syntactically complex multi-line cases would mostly really want whitespace cleanup anyway. Signed-off-by: Linus Torvalds

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51Z

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28Z

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

tracing: Fix checking of freed trace_event_file for hist files

2026-02-19T20:23:49Z

The event_hist_open() and event_hist_poll() functions currently retrieve a trace_event_file pointer from a file struct by invoking event_file_data(), which simply returns file->f_inode->i_private. The functions then check if the pointer is NULL to determine whether the event is still valid. This approach is flawed because i_private is assigned when an eventfs inode is allocated and remains set throughout its lifetime. Instead, the code should call event_file_file(), which checks for EVENT_FILE_FL_FREED. Using the incorrect access function may result in the code potentially opening a hist file for an event that is being removed or becoming stuck while polling on this file. Correct the access method to event_file_file() in both functions. Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Cc: Tom Zanussi Link: https://patch.msgid.link/20260219162737.314231-2-petr.pavlu@suse.com Fixes: 1bd13edbbed6 ("tracing/hist: Add poll(POLLIN) support on hist file") Signed-off-by: Petr Pavlu Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)

tracing: Move tracing_set_filter_buffering() into trace_events_hist.c

2026-02-09T02:01:11Z

The function tracing_set_filter_buffering() is only used in trace_events_hist.c. Move it to that file and make it static. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://patch.msgid.link/20260206195936.617080218@kernel.org Signed-off-by: Steven Rostedt (Google)

tracing: Up the hist stacktrace size from 16 to 31

2026-01-29T02:01:10Z

Recording stacktraces is very useful, but the size of 16 deep is very restrictive. For example, in seeing where tasks schedule out in a non running state, the following can be used: ~# cd /sys/kernel/tracing ~# echo 'hist:keys=common_stacktrace:vals=hitcount if prev_state & 3' > events/sched/sched_switch/trigger ~# cat events/sched/sched_switch/hist [..] { common_stacktrace: __schedule+0xdc0/0x1860 schedule+0x27/0xd0 schedule_timeout+0xb5/0x100 wait_for_completion+0x8a/0x140 xfs_buf_iowait+0x20/0xd0 [xfs] xfs_buf_read_map+0x103/0x250 [xfs] xfs_trans_read_buf_map+0x161/0x310 [xfs] xfs_btree_read_buf_block+0xa0/0x120 [xfs] xfs_btree_lookup_get_block+0xa3/0x1e0 [xfs] xfs_btree_lookup+0xea/0x530 [xfs] xfs_alloc_fixup_trees+0x72/0x570 [xfs] xfs_alloc_ag_vextent_size+0x67f/0x800 [xfs] xfs_alloc_vextent_iterate_ags.constprop.0+0x52/0x230 [xfs] xfs_alloc_vextent_start_ag+0x9d/0x1b0 [xfs] xfs_bmap_btalloc+0x2af/0x680 [xfs] xfs_bmapi_allocate+0xdb/0x2c0 [xfs] } hitcount: 1 [..] The above stops at 16 functions where knowing more would be useful. As the allocated storage for stacks is the same for strings, and that size is 256 bytes, there is a lot of space not being used for stacktraces. 16 * 8 = 128 Up the size to 31 (it requires the last slot to be zero, so it can't be 32). Also change the BUILD_BUG_ON() to allow the size of the stacktrace storage to be equal to the max size. One slot is used to hold the number of elements in the stack. BUILD_BUG_ON((HIST_STACKTRACE_DEPTH + 1) * sizeof(long) >= STR_VAR_LEN_MAX); Change that from ">=" to just ">", as now they are equal. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20260123105415.2be26bf4@gandalf.local.home Reviewed-by: Tom Zanussi Signed-off-by: Steven Rostedt (Google)

tracing: Have hist_debug show what function a field uses

2026-01-29T00:32:55Z

When CONFIG_HIST_TRIGGERS_DEBUG is enabled, each trace event has a "hist_debug" file that explains the histogram internal data. This is very useful for debugging histograms. One bit of data that was missing from this file was what function a histogram field uses to process its data. The hist_field structure now has a fn_num that is used by a switch statement in hist_fn_call() to call a function directly (to avoid spectre mitigations). Instead of displaying that number, create a string array that maps to the histogram function enums so that the function for a field may be displayed: ~# cat /sys/kernel/tracing/events/sched/sched_switch/hist_debug [..] hist_data: 0000000043d62762 n_vals: 2 n_keys: 1 n_fields: 3 val fields: hist_data->fields[0]: flags: VAL: HIST_FIELD_FL_HITCOUNT type: u64 size: 8 is_signed: 0 function: hist_field_counter() hist_data->fields[1]: flags: HIST_FIELD_FL_VAR var.name: __arg_3921_2 var.idx (into tracing_map_elt.vars[]): 0 type: unsigned long[] size: 128 is_signed: 0 function: hist_field_nop() key fields: hist_data->fields[2]: flags: HIST_FIELD_FL_KEY ftrace_event_field name: prev_pid type: pid_t size: 8 is_signed: 1 function: hist_field_s32() The "function:" field above is added. Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20260122203822.58df4d80@gandalf.local.home Reviewed-by: Tom Zanussi Tested-by: Tom Zanussi Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)