So far we silently convert negative return values from run() as
EXIT_FAILURE, which is how UNIX expects it. In many cases it would be
very useful for the caller to retrieve the actual error number we exit
with. Let's generically return that via sd_notify()'s ERRNO= attribute.
This means callers can set $NOTIFY_SOCKET and get the actual error
number delivered at their doorstep just like that.
This adds a new safe_fork() flag. If set the child process' fd 1 becomes
fd 2 of the caller. This is useful for invoking tools (such as various
mkfs/fsck implementations) that output status messages to stdout, but
which we invoke and don't want to pollute stdout with their output.
The actual burst limit is modified by the remaining disk space. This
isn't mentioned anywhere in the available documentation and might be a
source of surprise for an end user expecting certain behaviors.
If there is no boot menu timeout, pressing a key during boot should get
the boot menu displayed. However, on some systems the keyboard is not
initialized right away, which causes the menu to be inaccessible if no
timeout is specified.
To resolve this, if the error is "not ready" after the initial attempt of
detection, wait for 0.1 second and retry. This solves the problem
described above on all the tested systems.
The reason for just a single retry, and not retrying while "not ready",
is that some firmwares continue to return the "not ready" error on
every probe attempt if no key is pressed.
Signed-off-by: Leonid Bloch <lb.workbox@gmail.com>
We don't, the signal remains blocked. We use signalfd() to be able to
read the signal events without unblocking the signal.
While we are at it, mention that pthread_sigmask() is fine too.
We already refuse sd_event_add_signal() if the specified signal is not
blocked, let's do this also for sd_event_add_child(), since we might
need signalfd() to implement this, and this means the signal needs to be
blocked.
This adds support for watching for process exits via Linux new pidfd
concept. This makes watching processes and killing them race-free if
properly used, fixing a long-standing UNIX misdesign.
This patch adds implicit and explicit pidfd support to sd-event: if a
process shall be watched and is specified by PID we will now internally
create a pidfd for it and use that, if available. Alternatively a new
constructor for child process event sources is added that takes pidfds
as input.
Besides mere watching of child processes via pidfd two additional
features are added:
→ sd_event_source_send_child_signal() allows sending a signal to the
process being watched in the safest way possible (wrapping
the new pidfd_send_signal() syscall).
→ sd_event_source_set_child_process_own() allows marking a process
watched for destruction as soon as the event source is freed. This is
currently implemented in userspace, but hopefully will become a kernel
feature eventually.
Altogether this means an sd_event_source object is now a safe and stable
concept for referencing processes in race-free way, with automatic
fallback to pre-pidfd kernels.
Note that this patch adds support for this only to sd-event, not to PID
1. That's because PID 1 needs to use waitid(P_ALL) for reaping any
process that might get reparented to it. This currently semantically
conflicts with pidfd use for watching processes since we P_ALL is
undirected and thus might reap process earlier than the pidfd notifies
process end, which is hard to handle. The kernel will likely gain a
concept for excluding specific pidfds from P_ALL watching, as soon as
that is around we can start making use of this in PID 1 too.
This is not a new system call at all (since kernel 2.2), however it's
not exposed in glibc (a wrapper is exposed however in sigqueue(), but it
substantially simplifies the system call). Since we want a nice fallback
for sending signals on non-pidfd systems for pidfd_send_signal() let's
wrap rt_sigqueueinfo() since it takes the same siginfo_t parameter.
When running the program with udev_event_spawn it is possible to miss
output in stdout when the program exits causing the result to be empty
which can cause rules using the result to not function correctly.
This is due to the on_spawn_sigchld callback being processed while IO is
still pending and causing the event loop to exit.
To correct this the sigchld event source is made a lower priority than
the other event sources to ensure it is processed after IO. This
requires changing the IO event source to oneshot and re-enabling it when
valid data is read but not for EOF, this prevents the empty pipes
constantly generating IO events.
Reloading the SELinux label cache here enables a light-wight follow-up of a SELinux policy change, e.g. adding a label for a RuntimeDirectory.
Closes: #13363
