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riscv: ftrace: do not use stop_machine to update code

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Now it is safe to remove dependency from stop_machine() for us to patch
code in ftrace.

Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Link: https://lore.kernel.org/r/20250407180838.42877-6-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
This commit is contained in:
Andy Chiu 2025-04-08 02:08:30 +08:00 committed by Palmer Dabbelt
parent b2137c3b6d
commit 5aa4ef9558
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1 changed files with 10 additions and 54 deletions
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64
arch/riscv/kernel/ftrace.c
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@ -24,23 +24,13 @@ unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
return fentry_ip - MCOUNT_AUIPC_SIZE;
}
void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
void arch_ftrace_update_code(int command)
{
mutex_lock(&text_mutex);
/*
* The code sequences we use for ftrace can't be patched while the
* kernel is running, so we need to use stop_machine() to modify them
* for now. This doesn't play nice with text_mutex, we use this flag
* to elide the check.
*/
riscv_patch_in_stop_machine = true;
}
void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
{
riscv_patch_in_stop_machine = false;
command |= FTRACE_MAY_SLEEP;
ftrace_modify_all_code(command);
mutex_unlock(&text_mutex);
flush_icache_all();
}
static int __ftrace_modify_call(unsigned long source, unsigned long target, bool validate)
@ -129,51 +119,17 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
* before the write to function_trace_op later in the generic ftrace.
* If the sequence is not enforced, then an old ftrace_call_dest may
* race loading a new function_trace_op set in ftrace_modify_all_code
*
* If we are in stop_machine, then we don't need to call remote fence
* as there is no concurrent read-side of ftrace_call_dest.
*/
smp_wmb();
if (!irqs_disabled())
smp_call_function(ftrace_sync_ipi, NULL, 1);
/*
* Updating ftrace dpes not take stop_machine path, so irqs should not
* be disabled.
*/
WARN_ON(irqs_disabled());
smp_call_function(ftrace_sync_ipi, NULL, 1);
return 0;
}
struct ftrace_modify_param {
int command;
atomic_t cpu_count;
};
static int __ftrace_modify_code(void *data)
{
struct ftrace_modify_param *param = data;
if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
ftrace_modify_all_code(param->command);
/*
* Make sure the patching store is effective *before* we
* increment the counter which releases all waiting CPUs
* by using the release variant of atomic increment. The
* release pairs with the call to local_flush_icache_all()
* on the waiting CPU.
*/
atomic_inc_return_release(&param->cpu_count);
} else {
while (atomic_read(&param->cpu_count) <= num_online_cpus())
cpu_relax();
local_flush_icache_all();
}
return 0;
}
void arch_ftrace_update_code(int command)
{
struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
stop_machine(__ftrace_modify_code, &param, cpu_online_mask);
}
#else /* CONFIG_DYNAMIC_FTRACE */
unsigned long ftrace_call_adjust(unsigned long addr)
{