kernel/linux.git/include/linux/eventpoll.h, branch linux-5.11.y

kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE

2021-03-04T11:15:38+00:00

commit bfe3911a91047557eb0e620f95a370aee6a248c7 upstream. Userspace has discovered the functionality offered by SYS_kcmp and has started to depend upon it. In particular, Mesa uses SYS_kcmp for os_same_file_description() in order to identify when two fd (e.g. device or dmabuf) point to the same struct file. Since they depend on it for core functionality, lift SYS_kcmp out of the non-default CONFIG_CHECKPOINT_RESTORE into the selectable syscall category. Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to deduplicate the per-service file descriptor store. Note that some distributions such as Ubuntu are already enabling CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp. References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046 Signed-off-by: Chris Wilson Cc: Kees Cook Cc: Andy Lutomirski Cc: Will Drewry Cc: Andrew Morton Cc: Dave Airlie Cc: Daniel Vetter Cc: Lucas Stach Cc: Rasmus Villemoes Cc: Cyrill Gorcunov Cc: stable@vger.kernel.org Acked-by: Daniel Vetter # DRM depends on kcmp Acked-by: Rasmus Villemoes # systemd uses kcmp Reviewed-by: Cyrill Gorcunov Reviewed-by: Kees Cook Acked-by: Thomas Zimmermann Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@chris-wilson.co.uk Signed-off-by: Greg Kroah-Hartman

epoll: take epitem list out of struct file

2020-10-26T00:02:08+00:00

Move the head of epitem list out of struct file; for epoll ones it's moved into struct eventpoll (->refs there), for non-epoll - into the new object (struct epitem_head). In place of ->f_ep_links we leave a pointer to the list head (->f_ep). ->f_ep is protected by ->f_lock and it's zeroed as soon as the list of epitems becomes empty (that can happen only in ep_remove() by now). The list of files for reverse path check is *not* going through struct file now - it's a single-linked list going through epitem_head instances. It's terminated by ERR_PTR(-1) (== EP_UNACTIVE_POINTER), so the elements of list can be distinguished by head->next != NULL. epitem_head instances are allocated at ep_insert() time (by attach_epitem()) and freed either by ep_remove() (if it empties the set of epitems *and* epitem_head does not belong to the reverse path check list) or by clear_tfile_check_list() when the list is emptied (if the set of epitems is empty by that point). Allocations are done from a separate slab - minimal kmalloc() size is too large on some architectures. As the result, we trim struct file _and_ get rid of the games with temporary file references. Locking and barriers are interesting (aren't they always); see unlist_file() and ep_remove() for details. The non-obvious part is that ep_remove() needs to decide if it will be the one to free the damn thing *before* actually storing NULL to head->epitems.first - that's what smp_load_acquire is for in there. unlist_file() lockless path is safe, since we hit it only if we observe NULL in head->epitems.first and whoever had done that store is guaranteed to have observed non-NULL in head->next. IOW, their last access had been the store of NULL into ->epitems.first and we can safely free the sucker. OTOH, we are under rcu_read_lock() and both epitem and epitem->file have their freeing RCU-delayed. So if we see non-NULL ->epitems.first, we can grab ->f_lock (all epitems in there share the same struct file) and safely recheck the emptiness of ->epitems; again, ->next is still non-NULL, so ep_remove() couldn't have freed head yet. ->f_lock serializes us wrt ep_remove(); the rest is trivial. Note that once head->epitems becomes NULL, nothing can get inserted into it - the only remaining reference to head after that point is from the reverse path check list. Signed-off-by: Al Viro

convert ->f_ep_links/->fllink to hlist

2020-10-26T00:02:06+00:00

we don't care about the order of elements there Signed-off-by: Al Viro

eventpoll: support non-blocking do_epoll_ctl() calls

2020-01-29T22:45:47+00:00

Also make it available outside of epoll, along with the helper that decides if we need to copy the passed in epoll_event. Signed-off-by: Jens Axboe

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman

kcmp: fs/epoll: wrap kcmp code with CONFIG_CHECKPOINT_RESTORE

2017-07-12T23:26:01+00:00

kcmp syscall is build iif CONFIG_CHECKPOINT_RESTORE is selected, so wrap appropriate helpers in epoll code with the config to build it conditionally. Link: http://lkml.kernel.org/r/20170513083456.GG1881@uranus.lan Signed-off-by: Cyrill Gorcunov Reported-by: Andrew Morton Cc: Andrey Vagin Cc: Al Viro Cc: Pavel Emelyanov Cc: Michael Kerrisk Cc: Jason Baron Cc: Andy Lutomirski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kcmp: add KCMP_EPOLL_TFD mode to compare epoll target files

2017-07-12T23:26:01+00:00

With current epoll architecture target files are addressed with file_struct and file descriptor number, where the last is not unique. Moreover files can be transferred from another process via unix socket, added into queue and closed then so we won't find this descriptor in the task fdinfo list. Thus to checkpoint and restore such processes CRIU needs to find out where exactly the target file is present to add it into epoll queue. For this sake one can use kcmp call where some particular target file from the queue is compared with arbitrary file passed as an argument. Because epoll target files can have same file descriptor number but different file_struct a caller should explicitly specify the offset within. To test if some particular file is matching entry inside epoll one have to - fill kcmp_epoll_slot structure with epoll file descriptor, target file number and target file offset (in case if only one target is present then it should be 0) - call kcmp as kcmp(pid1, pid2, KCMP_EPOLL_TFD, fd, &kcmp_epoll_slot) - the kernel fetch file pointer matching file descriptor @fd of pid1 - lookups for file struct in epoll queue of pid2 and returns traditional 0,1,2 result for sorting purpose Link: http://lkml.kernel.org/r/20170424154423.511592110@gmail.com Signed-off-by: Cyrill Gorcunov Acked-by: Andrey Vagin Cc: Al Viro Cc: Pavel Emelyanov Cc: Michael Kerrisk Cc: Jason Baron Cc: Andy Lutomirski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48+00:00

Signed-off-by: David Howells Acked-by: Arnd Bergmann Acked-by: Thomas Gleixner Acked-by: Michael Kerrisk Acked-by: Paul E. McKenney Acked-by: Dave Jones

epoll: support for disabling items, and a self-test app

2012-10-05T18:05:00+00:00

Enhanced epoll_ctl to support EPOLL_CTL_DISABLE, which disables an epoll item. If epoll_ctl doesn't return -EBUSY in this case, it is then safe to delete the epoll item in a multi-threaded environment. Also added a new test_epoll self- test app to both demonstrate the need for this feature and test it. Signed-off-by: Paton J. Lewis Cc: Alexander Viro Cc: Jason Baron Cc: Paul Holland Cc: Davide Libenzi Cc: Michael Kerrisk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

PM: Rename CAP_EPOLLWAKEUP to CAP_BLOCK_SUSPEND

2012-07-17T19:37:27+00:00

As discussed in http://thread.gmane.org/gmane.linux.kernel/1249726/focus=1288990, the capability introduced in 4d7e30d98939a0340022ccd49325a3d70f7e0238 to govern EPOLLWAKEUP seems misnamed: this capability is about governing the ability to suspend the system, not using a particular API flag (EPOLLWAKEUP). We should make the name of the capability more general to encourage reuse in related cases. (Whether or not this capability should also be used to govern the use of /sys/power/wake_lock is a question that needs to be separately resolved.) This patch renames the capability to CAP_BLOCK_SUSPEND. In order to ensure that the old capability name doesn't make it out into the wild, could you please apply and push up the tree to ensure that it is incorporated for the 3.5 release. Signed-off-by: Michael Kerrisk Acked-by: Serge Hallyn Signed-off-by: Rafael J. Wysocki