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tracing: Place trace_pid_list logic into abstract functions
Instead of having the logic that does trace_pid_list open coded, wrap it in abstract functions. This will allow a rewrite of the logic that implements the trace_pid_list without affecting the users. Note, this causes a change in behavior. Every time a pid is written into the set_*_pid file, it creates a new list and uses RCU to update it. If pid_max is lowered, but there was a pid currently in the list that was higher than pid_max, those pids will now be removed on updating the list. The old behavior kept that from happening. The rewrite of the pid_list logic will no longer depend on pid_max, and will return the old behavior. Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
| /* | ||
| * Copyright (C) 2021 VMware Inc, Steven Rostedt <[email protected]> | ||
| */ | ||
| #include <linux/vmalloc.h> | ||
| #include <linux/slab.h> | ||
| #include "trace.h" | ||
|
|
||
| /** | ||
| * trace_pid_list_is_set - test if the pid is set in the list | ||
| * @pid_list: The pid list to test | ||
| * @pid: The pid to to see if set in the list. | ||
| * | ||
| * Tests if @pid is is set in the @pid_list. This is usually called | ||
| * from the scheduler when a task is scheduled. Its pid is checked | ||
| * if it should be traced or not. | ||
| * | ||
| * Return true if the pid is in the list, false otherwise. | ||
| */ | ||
| bool trace_pid_list_is_set(struct trace_pid_list *pid_list, unsigned int pid) | ||
| { | ||
| /* | ||
| * If pid_max changed after filtered_pids was created, we | ||
| * by default ignore all pids greater than the previous pid_max. | ||
| */ | ||
| if (pid >= pid_list->pid_max) | ||
| return false; | ||
|
|
||
| return test_bit(pid, pid_list->pids); | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_set - add a pid to the list | ||
| * @pid_list: The pid list to add the @pid to. | ||
| * @pid: The pid to add. | ||
| * | ||
| * Adds @pid to @pid_list. This is usually done explicitly by a user | ||
| * adding a task to be traced, or indirectly by the fork function | ||
| * when children should be traced and a task's pid is in the list. | ||
| * | ||
| * Return 0 on success, negative otherwise. | ||
| */ | ||
| int trace_pid_list_set(struct trace_pid_list *pid_list, unsigned int pid) | ||
| { | ||
| /* Sorry, but we don't support pid_max changing after setting */ | ||
| if (pid >= pid_list->pid_max) | ||
| return -EINVAL; | ||
|
|
||
| set_bit(pid, pid_list->pids); | ||
|
|
||
| return 0; | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_clear - remove a pid from the list | ||
| * @pid_list: The pid list to remove the @pid from. | ||
| * @pid: The pid to remove. | ||
| * | ||
| * Removes @pid from @pid_list. This is usually done explicitly by a user | ||
| * removing tasks from tracing, or indirectly by the exit function | ||
| * when a task that is set to be traced exits. | ||
| * | ||
| * Return 0 on success, negative otherwise. | ||
| */ | ||
| int trace_pid_list_clear(struct trace_pid_list *pid_list, unsigned int pid) | ||
| { | ||
| /* Sorry, but we don't support pid_max changing after setting */ | ||
| if (pid >= pid_list->pid_max) | ||
| return -EINVAL; | ||
|
|
||
| clear_bit(pid, pid_list->pids); | ||
|
|
||
| return 0; | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_next - return the next pid in the list | ||
| * @pid_list: The pid list to examine. | ||
| * @pid: The pid to start from | ||
| * @next: The pointer to place the pid that is set starting from @pid. | ||
| * | ||
| * Looks for the next consecutive pid that is in @pid_list starting | ||
| * at the pid specified by @pid. If one is set (including @pid), then | ||
| * that pid is placed into @next. | ||
| * | ||
| * Return 0 when a pid is found, -1 if there are no more pids included. | ||
| */ | ||
| int trace_pid_list_next(struct trace_pid_list *pid_list, unsigned int pid, | ||
| unsigned int *next) | ||
| { | ||
| pid = find_next_bit(pid_list->pids, pid_list->pid_max, pid); | ||
|
|
||
| if (pid < pid_list->pid_max) { | ||
| *next = pid; | ||
| return 0; | ||
| } | ||
| return -1; | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_first - return the first pid in the list | ||
| * @pid_list: The pid list to examine. | ||
| * @pid: The pointer to place the pid first found pid that is set. | ||
| * | ||
| * Looks for the first pid that is set in @pid_list, and places it | ||
| * into @pid if found. | ||
| * | ||
| * Return 0 when a pid is found, -1 if there are no pids set. | ||
| */ | ||
| int trace_pid_list_first(struct trace_pid_list *pid_list, unsigned int *pid) | ||
| { | ||
| unsigned int first; | ||
|
|
||
| first = find_first_bit(pid_list->pids, pid_list->pid_max); | ||
|
|
||
| if (first < pid_list->pid_max) { | ||
| *pid = first; | ||
| return 0; | ||
| } | ||
| return -1; | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_alloc - create a new pid_list | ||
| * | ||
| * Allocates a new pid_list to store pids into. | ||
| * | ||
| * Returns the pid_list on success, NULL otherwise. | ||
| */ | ||
| struct trace_pid_list *trace_pid_list_alloc(void) | ||
| { | ||
| struct trace_pid_list *pid_list; | ||
|
|
||
| pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL); | ||
| if (!pid_list) | ||
| return NULL; | ||
|
|
||
| pid_list->pid_max = READ_ONCE(pid_max); | ||
|
|
||
| pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3); | ||
| if (!pid_list->pids) { | ||
| kfree(pid_list); | ||
| return NULL; | ||
| } | ||
| return pid_list; | ||
| } | ||
|
|
||
| /** | ||
| * trace_pid_list_free - Frees an allocated pid_list. | ||
| * | ||
| * Frees the memory for a pid_list that was allocated. | ||
| */ | ||
| void trace_pid_list_free(struct trace_pid_list *pid_list) | ||
| { | ||
| if (!pid_list) | ||
| return; | ||
|
|
||
| vfree(pid_list->pids); | ||
| kfree(pid_list); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,13 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
|
|
||
| /* Do not include this file directly. */ | ||
|
|
||
| #ifndef _TRACE_INTERNAL_PID_LIST_H | ||
| #define _TRACE_INTERNAL_PID_LIST_H | ||
|
|
||
| struct trace_pid_list { | ||
| int pid_max; | ||
| unsigned long *pids; | ||
| }; | ||
|
|
||
| #endif /* _TRACE_INTERNAL_PID_LIST_H */ |
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