Re: [PATCH v2 2/9] backends/tpm: Replace qemu_mutex_lock calls with QEMU_LOCK_GUARD

[Christophe de Dinechin <dinechin@redhat.com>]

On 2021-05-06 at 15:37 CEST, Philippe Mathieu-Daudé wrote...
> Simplify the tpm_emulator_ctrlcmd() handler by replacing a pair of
> qemu_mutex_lock/qemu_mutex_unlock calls by the WITH_QEMU_LOCK_GUARD
> macro.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  backends/tpm/tpm_emulator.c | 34 +++++++++++++++-------------------
>  1 file changed, 15 insertions(+), 19 deletions(-)
>
> diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
> index a012adc1934..e5f1063ab6c 100644
> --- a/backends/tpm/tpm_emulator.c
> +++ b/backends/tpm/tpm_emulator.c
> @@ -30,6 +30,7 @@
>  #include "qemu/error-report.h"
>  #include "qemu/module.h"
>  #include "qemu/sockets.h"
> +#include "qemu/lockable.h"
>  #include "io/channel-socket.h"
>  #include "sysemu/tpm_backend.h"
>  #include "sysemu/tpm_util.h"
> @@ -124,31 +125,26 @@ static int tpm_emulator_ctrlcmd(TPMEmulator *tpm, unsigned long cmd, void *msg,
>      uint32_t cmd_no = cpu_to_be32(cmd);
>      ssize_t n = sizeof(uint32_t) + msg_len_in;
>      uint8_t *buf = NULL;
> -    int ret = -1;
>
> -    qemu_mutex_lock(&tpm->mutex);
> +    WITH_QEMU_LOCK_GUARD(&tpm->mutex) {
> +        buf = g_alloca(n);
> +        memcpy(buf, &cmd_no, sizeof(cmd_no));
> +        memcpy(buf + sizeof(cmd_no), msg, msg_len_in);
>
> -    buf = g_alloca(n);
> -    memcpy(buf, &cmd_no, sizeof(cmd_no));
> -    memcpy(buf + sizeof(cmd_no), msg, msg_len_in);
> -
> -    n = qemu_chr_fe_write_all(dev, buf, n);
> -    if (n <= 0) {
> -        goto end;
> -    }
> -
> -    if (msg_len_out != 0) {
> -        n = qemu_chr_fe_read_all(dev, msg, msg_len_out);
> +        n = qemu_chr_fe_write_all(dev, buf, n);
>          if (n <= 0) {
> -            goto end;
> +            return -1;
> +        }
> +
> +        if (msg_len_out != 0) {
> +            n = qemu_chr_fe_read_all(dev, msg, msg_len_out);
> +            if (n <= 0) {
> +                return -1;
> +            }
>          }
>      }
>
> -    ret = 0;
> -
> -end:
> -    qemu_mutex_unlock(&tpm->mutex);
> -    return ret;
> +    return 0;
>  }
>
>  static int tpm_emulator_unix_tx_bufs(TPMEmulator *tpm_emu,

I really like the improvement, but it looks like it does not belong to the
top-level series (i.e. not related to replacing alloca() by g_malloc()).

Reviewed-by: Christophe de Dinechin <dinechin@redhat.com>

--
Cheers,
Christophe de Dinechin (IRC c3d)