On Tue, May 09, 2023 at 10:36:42PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
>
> Guenter reported a lockdep splat that appears to have been present for a
> while in v6.1.y & the backports of the riscv_patch_in_stop_machine dance
> did nothing to help here, as the lock is not being taken when
> patch_text_nosync() is called in riscv_cpufeature_patch_func().
> Add the lock/unlock; elide the splat.
>
> Fixes: c15ac4fd60d5 ("riscv/ftrace: Add dynamic function tracer support")
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Guenter
> ---
> arch/riscv/kernel/cpufeature.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 694267d1fe81..fd1238df6149 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -9,6 +9,7 @@
> #include <linux/bitmap.h>
> #include <linux/ctype.h>
> #include <linux/libfdt.h>
> +#include <linux/memory.h>
> #include <linux/module.h>
> #include <linux/of.h>
> #include <asm/alternative.h>
> @@ -316,8 +317,11 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
> }
>
> tmp = (1U << alt->errata_id);
> - if (cpu_req_feature & tmp)
> + if (cpu_req_feature & tmp) {
> + mutex_lock(&text_mutex);
> patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
> + mutex_unlock(&text_mutex);
> + }
> }
> }
> #endif
> --
> 2.39.2
>
