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![Steven Rostedt (VMware)](/assets/img/avatar_default.png)
In trace_test_and_set_recursion(), current->trace_recursion is placed into a variable, and that variable should be used for the processing, as there's no reason to dereference current multiple times. On trace_clear_recursion(), current->trace_recursion is modified and there's no reason to copy it over to a variable. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
232 lines
6.8 KiB
C
232 lines
6.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_TRACE_RECURSION_H
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#define _LINUX_TRACE_RECURSION_H
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#ifdef CONFIG_TRACING
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/* Only current can touch trace_recursion */
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/*
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* For function tracing recursion:
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* The order of these bits are important.
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*
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* When function tracing occurs, the following steps are made:
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* If arch does not support a ftrace feature:
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* call internal function (uses INTERNAL bits) which calls...
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* If callback is registered to the "global" list, the list
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* function is called and recursion checks the GLOBAL bits.
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* then this function calls...
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* The function callback, which can use the FTRACE bits to
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* check for recursion.
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*
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* Now if the arch does not support a feature, and it calls
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* the global list function which calls the ftrace callback
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* all three of these steps will do a recursion protection.
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* There's no reason to do one if the previous caller already
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* did. The recursion that we are protecting against will
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* go through the same steps again.
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*
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* To prevent the multiple recursion checks, if a recursion
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* bit is set that is higher than the MAX bit of the current
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* check, then we know that the check was made by the previous
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* caller, and we can skip the current check.
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*/
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enum {
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/* Function recursion bits */
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TRACE_FTRACE_BIT,
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TRACE_FTRACE_NMI_BIT,
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TRACE_FTRACE_IRQ_BIT,
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TRACE_FTRACE_SIRQ_BIT,
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/* INTERNAL_BITs must be greater than FTRACE_BITs */
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TRACE_INTERNAL_BIT,
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TRACE_INTERNAL_NMI_BIT,
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TRACE_INTERNAL_IRQ_BIT,
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TRACE_INTERNAL_SIRQ_BIT,
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TRACE_BRANCH_BIT,
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/*
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* Abuse of the trace_recursion.
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* As we need a way to maintain state if we are tracing the function
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* graph in irq because we want to trace a particular function that
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* was called in irq context but we have irq tracing off. Since this
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* can only be modified by current, we can reuse trace_recursion.
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*/
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TRACE_IRQ_BIT,
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/* Set if the function is in the set_graph_function file */
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TRACE_GRAPH_BIT,
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/*
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* In the very unlikely case that an interrupt came in
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* at a start of graph tracing, and we want to trace
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* the function in that interrupt, the depth can be greater
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* than zero, because of the preempted start of a previous
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* trace. In an even more unlikely case, depth could be 2
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* if a softirq interrupted the start of graph tracing,
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* followed by an interrupt preempting a start of graph
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* tracing in the softirq, and depth can even be 3
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* if an NMI came in at the start of an interrupt function
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* that preempted a softirq start of a function that
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* preempted normal context!!!! Luckily, it can't be
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* greater than 3, so the next two bits are a mask
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* of what the depth is when we set TRACE_GRAPH_BIT
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*/
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TRACE_GRAPH_DEPTH_START_BIT,
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TRACE_GRAPH_DEPTH_END_BIT,
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/*
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* To implement set_graph_notrace, if this bit is set, we ignore
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* function graph tracing of called functions, until the return
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* function is called to clear it.
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*/
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TRACE_GRAPH_NOTRACE_BIT,
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/*
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* When transitioning between context, the preempt_count() may
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* not be correct. Allow for a single recursion to cover this case.
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*/
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TRACE_TRANSITION_BIT,
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/* Used to prevent recursion recording from recursing. */
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TRACE_RECORD_RECURSION_BIT,
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};
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#define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0)
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#define trace_recursion_clear(bit) do { (current)->trace_recursion &= ~(1<<(bit)); } while (0)
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#define trace_recursion_test(bit) ((current)->trace_recursion & (1<<(bit)))
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#define trace_recursion_depth() \
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(((current)->trace_recursion >> TRACE_GRAPH_DEPTH_START_BIT) & 3)
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#define trace_recursion_set_depth(depth) \
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do { \
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current->trace_recursion &= \
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~(3 << TRACE_GRAPH_DEPTH_START_BIT); \
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current->trace_recursion |= \
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((depth) & 3) << TRACE_GRAPH_DEPTH_START_BIT; \
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} while (0)
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#define TRACE_CONTEXT_BITS 4
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#define TRACE_FTRACE_START TRACE_FTRACE_BIT
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#define TRACE_FTRACE_MAX ((1 << (TRACE_FTRACE_START + TRACE_CONTEXT_BITS)) - 1)
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#define TRACE_LIST_START TRACE_INTERNAL_BIT
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#define TRACE_LIST_MAX ((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
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#define TRACE_CONTEXT_MASK TRACE_LIST_MAX
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/*
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* Used for setting context
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* NMI = 0
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* IRQ = 1
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* SOFTIRQ = 2
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* NORMAL = 3
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*/
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enum {
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TRACE_CTX_NMI,
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TRACE_CTX_IRQ,
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TRACE_CTX_SOFTIRQ,
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TRACE_CTX_NORMAL,
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};
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static __always_inline int trace_get_context_bit(void)
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{
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unsigned long pc = preempt_count();
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if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
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return TRACE_CTX_NORMAL;
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else
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return pc & NMI_MASK ? TRACE_CTX_NMI :
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pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ;
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}
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#ifdef CONFIG_FTRACE_RECORD_RECURSION
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extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
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# define do_ftrace_record_recursion(ip, pip) \
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do { \
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if (!trace_recursion_test(TRACE_RECORD_RECURSION_BIT)) { \
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trace_recursion_set(TRACE_RECORD_RECURSION_BIT); \
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ftrace_record_recursion(ip, pip); \
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trace_recursion_clear(TRACE_RECORD_RECURSION_BIT); \
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} \
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} while (0)
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#else
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# define do_ftrace_record_recursion(ip, pip) do { } while (0)
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#endif
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static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
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int start, int max)
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{
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unsigned int val = READ_ONCE(current->trace_recursion);
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int bit;
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/* A previous recursion check was made */
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if ((val & TRACE_CONTEXT_MASK) > max)
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return 0;
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bit = trace_get_context_bit() + start;
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if (unlikely(val & (1 << bit))) {
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/*
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* It could be that preempt_count has not been updated during
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* a switch between contexts. Allow for a single recursion.
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*/
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bit = TRACE_TRANSITION_BIT;
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if (val & (1 << bit)) {
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do_ftrace_record_recursion(ip, pip);
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return -1;
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}
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} else {
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/* Normal check passed, clear the transition to allow it again */
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val &= ~(1 << TRACE_TRANSITION_BIT);
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}
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val |= 1 << bit;
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current->trace_recursion = val;
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barrier();
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return bit + 1;
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}
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static __always_inline void trace_clear_recursion(int bit)
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{
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if (!bit)
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return;
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barrier();
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bit--;
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trace_recursion_clear(bit);
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}
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/**
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* ftrace_test_recursion_trylock - tests for recursion in same context
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*
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* Use this for ftrace callbacks. This will detect if the function
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* tracing recursed in the same context (normal vs interrupt),
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*
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* Returns: -1 if a recursion happened.
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* >= 0 if no recursion
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*/
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static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
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unsigned long parent_ip)
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{
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return trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX);
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}
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/**
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* ftrace_test_recursion_unlock - called when function callback is complete
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* @bit: The return of a successful ftrace_test_recursion_trylock()
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*
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* This is used at the end of a ftrace callback.
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*/
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static __always_inline void ftrace_test_recursion_unlock(int bit)
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{
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trace_clear_recursion(bit);
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}
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#endif /* CONFIG_TRACING */
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#endif /* _LINUX_TRACE_RECURSION_H */
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