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sd-event: handle kernels that set CONFIG_PSI_DEFAULT_DISABLED more gracefully

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If CONFIG_PSI_DEFAULT_DISABLED is set in the kernel, then the PSI files
will be there, and you can open them, but read()/write() will fail.
Which is terrible, since that happens so late. But anyway, handle this
gracefully.
This commit is contained in:
Lennart Poettering
2023-02-27 19:05:19 +01:00
committed by Luca Boccassi
parent 68a5526734
commit 9897f5ddea
1 changed files with 11 additions and 2 deletions
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13
src/libsystemd/sd-event/sd-event.c
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@@ -4000,8 +4000,17 @@ static int source_memory_pressure_write(sd_event_source *s) {
if (s->memory_pressure.write_buffer_size > 0) {
n = write(s->memory_pressure.fd, s->memory_pressure.write_buffer, s->memory_pressure.write_buffer_size);
if (n < 0) {
if (!ERRNO_IS_TRANSIENT(errno))
return -errno;
if (!ERRNO_IS_TRANSIENT(errno)) {
/* If kernel is built with CONFIG_PSI_DEFAULT_DISABLED it will expose PSI
* files, but then generates EOPNOSUPP on read() and write() (instead of on
* open()!). This sucks hard, since we can only detect this kind of failure
* so late. Let's make the best of it, and turn off the event source like we
* do for failed event source handlers. */
log_debug_errno(errno, "Writing memory pressure settings to kernel failed, disabling memory pressure event source: %m");
assert_se(sd_event_source_set_enabled(s, SD_EVENT_OFF) >= 0);
return 0;
}
n = 0;
}