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author | Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> | 2020-04-24 10:53:46 +0200 |
---|---|---|
committer | Lennart Poettering <lennart@poettering.net> | 2020-04-28 09:00:25 +0200 |
commit | 7229ec02ab3a7f498b93158b500e697838ccdd9b (patch) | |
tree | 34a6ec3920299e3fd5cfca1a3af743b9632ec930 | |
parent | 4b6d94a1e59b75c8623a0eaea49cc7ff26c8b820 (diff) | |
download | systemd-7229ec02ab3a7f498b93158b500e697838ccdd9b.tar.gz |
efivars: retry open and read operations
On my laptop (Lenovo X1carbo 4th) I very occasionally see test-boot-timestamps
fail with this tb:
262/494 test-boot-timestamps FAIL 0.7348453998565674 s (killed by signal 6 SIGABRT)
08:12:48 SYSTEMD_LANGUAGE_FALLBACK_MAP='/home/zbyszek/src/systemd/src/locale/language-fallback-map' SYSTEMD_KBD_MODEL_MAP='/home/zbyszek/src/systemd/src/locale/kbd-model-map' PATH='/home/zbyszek/src/systemd/build:/home/zbyszek/.local/bin:/usr/lib64/qt-3.3/bin:/usr/share/Modules/bin:/usr/condabin:/usr/lib64/ccache:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/home/zbyszek/bin:/var/lib/snapd/snap/bin' /home/zbyszek/src/systemd/build/test-boot-timestamps
--- stderr ---
Failed to read $container of PID 1, ignoring: Permission denied
Found container virtualization none.
Failed to get SystemdOptions EFI variable, ignoring: Interrupted system call
Failed to read ACPI FPDT: Permission denied
Failed to read LoaderTimeInitUSec: Interrupted system call
Failed to read EFI loader data: Interrupted system call
Assertion 'q >= 0' failed at src/test/test-boot-timestamps.c:84, function main(). Aborting.
Normally it takes ~0.02s, but here there's a slowdown to 0.73 and things fail with EINTR.
This happens only occasionally, and I haven't been able to capture a strace.
It would be to ignore that case in test-boot-timestamps or always translate
EINTR to -ENODATA. Nevertheless, I think it's better to retry, since this gives
as more resilient behaviour and avoids a transient failure.
See
https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75
and
https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd.
-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; } |