As the documentation explained, ftrace_test_recursion_trylock()
and ftrace_test_recursion_unlock() were supposed to disable and
enable preemption properly, however currently this work is done
outside of the function, which could be missing by mistake.
And since the internal using of trace_test_and_set_recursion()
and trace_clear_recursion() also require preemption disabled, we
can just merge the logical.
This patch will make sure the preemption has been disabled when
trace_test_and_set_recursion() return bit >= 0, and
trace_clear_recursion() will enable the preemption if previously
enabled.
Link: https://lkml.kernel.org/r/13bde807-779c-aa4c-0672-20515ae365ea@linux.alibaba.com
CC: Petr Mladek <pmladek@suse.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Jisheng Zhang <jszhang@kernel.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Miroslav Benes <mbenes@suse.cz>
Reported-by: Abaci <abaci@linux.alibaba.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
[ Removed extra line in comment - SDR ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (!p) {
p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE));
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
}
__this_cpu_write(current_kprobe, NULL);
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
return;
regs = ftrace_get_regs(fregs);
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)nip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
if (bit < 0)
return;
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
if (bit < 0)
return;
- preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
__this_cpu_write(current_kprobe, NULL);
}
out:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
# define do_ftrace_record_recursion(ip, pip) do { } while (0)
#endif
+/*
+ * Preemption is promised to be disabled when return bit >= 0.
+ */
static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
int start, int max)
{
current->trace_recursion = val;
barrier();
+ preempt_disable_notrace();
+
return bit + 1;
}
+/*
+ * Preemption will be enabled (if it was previously enabled).
+ */
static __always_inline void trace_clear_recursion(int bit)
{
if (!bit)
return;
+ preempt_enable_notrace();
barrier();
bit--;
trace_recursion_clear(bit);
* tracing recursed in the same context (normal vs interrupt),
*
* Returns: -1 if a recursion happened.
- * >= 0 if no recursion
+ * >= 0 if no recursion.
*/
static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
unsigned long parent_ip)
ops = container_of(fops, struct klp_ops, fops);
+ /*
+ * The ftrace_test_recursion_trylock() will disable preemption,
+ * which is required for the variant of synchronize_rcu() that is
+ * used to allow patching functions where RCU is not watching.
+ * See klp_synchronize_transition() for more details.
+ */
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (WARN_ON_ONCE(bit < 0))
return;
- /*
- * A variant of synchronize_rcu() is used to allow patching functions
- * where RCU is not watching, see klp_synchronize_transition().
- */
- preempt_disable_notrace();
func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
stack_node);
klp_arch_set_pc(fregs, (unsigned long)func->new_func);
unlock:
- preempt_enable_notrace();
ftrace_test_recursion_unlock(bit);
}
struct ftrace_ops *op;
int bit;
+ /*
+ * The ftrace_test_and_set_recursion() will disable preemption,
+ * which is required since some of the ops may be dynamically
+ * allocated, they must be freed after a synchronize_rcu().
+ */
bit = trace_test_and_set_recursion(ip, parent_ip, TRACE_LIST_START, TRACE_LIST_MAX);
if (bit < 0)
return;
- /*
- * Some of the ops may be dynamically allocated,
- * they must be freed after a synchronize_rcu().
- */
- preempt_disable_notrace();
-
do_for_each_ftrace_op(op, ftrace_ops_list) {
/* Stub functions don't need to be called nor tested */
if (op->flags & FTRACE_OPS_FL_STUB)
}
} while_for_each_ftrace_op(op);
out:
- preempt_enable_notrace();
trace_clear_recursion(bit);
}
if (bit < 0)
return;
- preempt_disable_notrace();
-
if (!(op->flags & FTRACE_OPS_FL_RCU) || rcu_is_watching())
op->func(ip, parent_ip, op, fregs);
- preempt_enable_notrace();
trace_clear_recursion(bit);
}
NOKPROBE_SYMBOL(ftrace_ops_assist_func);
return;
trace_ctx = tracing_gen_ctx();
- preempt_disable_notrace();
cpu = smp_processor_id();
data = per_cpu_ptr(tr->array_buffer.data, cpu);
trace_function(tr, ip, parent_ip, trace_ctx);
ftrace_test_recursion_unlock(bit);
- preempt_enable_notrace();
}
#ifdef CONFIG_UNWINDER_ORC
if (bit < 0)
return;
- preempt_disable_notrace();
-
cpu = smp_processor_id();
data = per_cpu_ptr(tr->array_buffer.data, cpu);
if (atomic_read(&data->disabled))
out:
ftrace_test_recursion_unlock(bit);
- preempt_enable_notrace();
}
static void
projects / kernel.git / commitdiff