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It seems commit 4a9d4b024a31 ("switch fput to task_work_add") re-
introduced the problem addressed in 944be0b22472 ("close_files(): add
scheduling point")
If a server process with a lot of files (say 2 million tcp sockets) is
killed, we can spend a lot of time in task_work_run() and trigger a soft
lockup.
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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It doesn't matter on normal return to userland path (we'll recheck the
NOTIFY_RESUME flag anyway), but in case of exit_task_work() we'll
need that as soon as we get callbacks capable of triggering more
task_work_add().
Signed-off-by: Al Viro <[email protected]>
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... and get rid of PF_EXITING check in task_work_add().
Signed-off-by: Al Viro <[email protected]>
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task_work and rcu_head are identical now; merge them (calling the result
struct callback_head, rcu_head #define'd to it), kill separate allocation
in security/keys since we can just use cred->rcu now.
Signed-off-by: Al Viro <[email protected]>
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layout based on Oleg's suggestion; single-linked list,
task->task_works points to the last element, forward pointer
from said last element points to head. I'd still prefer
much more regular scheme with two pointers in task_work,
but...
Signed-off-by: Al Viro <[email protected]>
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Provide a simple mechanism that allows running code in the (nonatomic)
context of the arbitrary task.
The caller does task_work_add(task, task_work) and this task executes
task_work->func() either from do_notify_resume() or from do_exit(). The
callback can rely on PF_EXITING to detect the latter case.
"struct task_work" can be embedded in another struct, still it has "void
*data" to handle the most common/simple case.
This allows us to kill the ->replacement_session_keyring hack, and
potentially this can have more users.
Performance-wise, this adds 2 "unlikely(!hlist_empty())" checks into
tracehook_notify_resume() and do_exit(). But at the same time we can
remove the "replacement_session_keyring != NULL" checks from
arch/*/signal.c and exit_creds().
Note: task_work_add/task_work_run abuses ->pi_lock. This is only because
this lock is already used by lookup_pi_state() to synchronize with
do_exit() setting PF_EXITING. Fortunately the scope of this lock in
task_work.c is really tiny, and the code is unlikely anyway.
Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: David Howells <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Richard Kuo <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: David Smith <[email protected]>
Cc: "Frank Ch. Eigler" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Larry Woodman <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Al Viro <[email protected]>
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