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basic/efivars: try re-reading efivars without delay first

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Quoting https://github.com/systemd/systemd/issues/14828#issuecomment-635212615:

> [kernel uses] msleep_interruptible() and that means when the process receives
> any kind of signal masked or not this will abort with EINTR.  systemd-logind
> gets signals from the TTY layer all the time though.

> Here's what might be happening: while logind reads the EFI stuff it gets a
> series of signals from the TTY layer, which causes the read() to be aborted
> with EINTR, which means logind will wait 50ms and retry. Which will be
> aborted again, and so on, until quite some time passed. If we'd not wait for
> the 50ms otoh we wouldn't wait so long, as then on each signal we'd
> immediately retry again.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-05-31 12:16:57 +02:00 committed by Lennart Poettering
parent 75f6d5d87e
commit eee9b30af4
1 changed files with 5 additions and 3 deletions
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8
src/basic/efivars.c
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@ -25,7 +25,8 @@
#if ENABLE_EFI
/* Reads from efivarfs sometimes fail with EINTR. Retry that many times. */
#define EFI_N_RETRIES 5
#define EFI_N_RETRIES_NO_DELAY 20
#define EFI_N_RETRIES_TOTAL 25
#define EFI_RETRY_DELAY (50 * USEC_PER_MSEC)
char* efi_variable_path(sd_id128_t vendor, const char *name) {
@ -101,10 +102,11 @@ int efi_get_variable(
log_debug_errno(errno, "Reading from \"%s\" failed: %m", p);
if (errno != EINTR)
return -errno;
if (try >= EFI_N_RETRIES)
if (try >= EFI_N_RETRIES_TOTAL)
return -EBUSY;
(void) usleep(EFI_RETRY_DELAY);
if (try >= EFI_N_RETRIES_NO_DELAY)
(void) usleep(EFI_RETRY_DELAY);
}
if (n != sizeof(a))