pidfd: tmp process is waited upon by correct process #2505
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
avagin
reviewed
Nov 6, 2024
avagin
reviewed
Nov 6, 2024
bsach64
force-pushed
the
common-dead
branch
3 times, most recently
from
e7303de
to
1a00bf7
Compare
mihalicyn
reviewed
Nov 8, 2024
|
LGTM |
mihalicyn
approved these changes
Nov 12, 2024
There was a problem hiding this comment.
I played with this PR locally and tried to make a deadlock. By combining pipe+pidfd in that way so one process became "master" (the one who restores pidfd or pipe pair) while another one became "slave" (the one who received fd through TRANSPORT_FD socket). But taking into account the fact that recv_desc_from_peer is non-blocking call and it can return 1 (which means "please retry later") we are on the safe side.
LGTM.
|
I'll do some small adjustments in this PR to fix code style issues so we can merge it today. Upd: have done. |
Currently, the `waitpid()` call on the tmp process can be made by a process which is not its parent. This causes restore to fail. This patch instead selects one process to create the tmp process and open all the fds that point to it. These fds are sent to the correct process(es). Fixes: checkpoint-restore#2496 Signed-off-by: Andrei Vagin <[email protected]> Signed-off-by: Bhavik Sachdev <[email protected]>
We have multiple processes open a pidfd to a common dead process. After C/R we check that the inode numbers for these pidfds are equal or not. Signed-off-by: Bhavik Sachdev <[email protected]>
mihalicyn
force-pushed
the
common-dead
branch
from
1a00bf7
to
54b8bd0
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes: #2496
This patch ensures that the process that created the tmp process is the one that kills and waits for it after all pidfds have been opened. We do this by keeping track of each process that has to open a pidfd for the tmp process and the number of pidfds it has to open.
Thing I am unsure about need to dump the pid of the process that opened the pidfd. (This might be available from some where else)