diff options
| -rw-r--r-- | src/basic/efivars.c | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/src/basic/efivars.c b/src/basic/efivars.c index 502c3a0c44..aa08ad2e27 100644 --- a/src/basic/efivars.c +++ b/src/basic/efivars.c @@ -24,6 +24,10 @@ #if ENABLE_EFI +/* Reads from efivarfs sometimes fail with EINTR. Retry that many times. */ +#define EFI_N_RETRIES 5 +#define EFI_RETRY_DELAY (50 * USEC_PER_MSEC) + char* efi_variable_path(sd_id128_t vendor, const char *name) { char *p; @@ -56,8 +60,8 @@ int efi_get_variable( return -ENOMEM; if (!ret_value && !ret_size && !ret_attribute) { - /* If caller is not interested in anything, just check if the variable exists and is readable - * to us. */ + /* If caller is not interested in anything, just check if the variable exists and is + * readable. */ if (access(p, R_OK) < 0) return -errno; @@ -66,7 +70,7 @@ int efi_get_variable( fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (fd < 0) - return -errno; + return log_debug_errno(errno, "open(\"%s\") failed: %m", p); if (fstat(fd, &st) < 0) return -errno; @@ -76,9 +80,26 @@ int efi_get_variable( return -E2BIG; if (ret_value || ret_attribute) { - n = read(fd, &a, sizeof(a)); - if (n < 0) - return -errno; + /* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll + * occasionally fail with EINTR here. A slowdown is better than a failure for us, so + * retry a few times and eventually fail with -EBUSY. + * + * See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75 + * and + * https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd. + */ + for (unsigned try = 0;; try++) { + n = read(fd, &a, sizeof(a)); + if (n >= 0) + break; + log_debug_errno(errno, "read from \"%s\" failed: %m", p); + if (errno != EINTR) + return -errno; + if (try >= EFI_N_RETRIES) + return -EBUSY; + usleep(EFI_RETRY_DELAY); + } + if (n != sizeof(a)) return -EIO; } |