Currently kernel threads use sigprocmask(SIG_BLOCK) to protect against
signals. This doesn't prevent the signal delivery, this only blocks
signal_wake_up(). Every "killall -33 kthreadd" means a "struct siginfo"
leak.
Change kthreadd_setup() to set all handlers to SIG_IGN instead of blocking
them (make a new helper ignore_signals() for that). If the kernel thread
needs some signal, it should use allow_signal() anyway, and in that case it
should not use CLONE_SIGHAND.
Note that we can't change daemonize() (should die!) in the same way,
because it can be used along with CLONE_SIGHAND. This means that
allow_signal() still should unblock the signal to work correctly with
daemonize()ed threads.
However, disallow_signal() doesn't block the signal any longer but ignores
it.
NOTE: with or without this patch the kernel threads are not protected from
handle_stop_signal(), this seems harmless, but not good.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently there is a circular reference between work queue initialization
and kthread initialization. This prevents the kthread infrastructure from
initializing until after work queues have been initialized.
We want the properties of tasks created with kthread_create to be as close
as possible to the init_task and to not be contaminated by user processes.
The later we start our kthreadd that creates these tasks the harder it is
to avoid contamination from user processes and the more of a mess we have
to clean up because the defaults have changed on us.
So this patch modifies the kthread support to not use work queues but to
instead use a simple list of structures, and to have kthreadd start from
init_task immediately after our kernel thread that execs /sbin/init.
By being a true child of init_task we only have to change those process
settings that we want to have different from init_task, such as our process
name, the cpus that are allowed, blocking all signals and setting SIGCHLD
to SIG_IGN so that all of our children are reaped automatically.
By being a true child of init_task we also naturally get our ppid set to 0
and do not wind up as a child of PID == 1. Ensuring that tasks generated
by kthread_create will not slow down the functioning of the wait family of
functions.
[akpm@linux-foundation.org: use interruptible sleeps]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A variety of (mostly) innocuous fixes to the embedded kernel-doc content in
source files, including:
* make multi-line initial descriptions single line
* denote some function names, constants and structs as such
* change erroneous opening '/*' to '/**' in a few places
* reword some text for clarity
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.
For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.
To make this work, an extra flag is introduced into the management side of the
work_struct. This governs auto-release of the structure upon execution.
Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function. This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated.. This is a
problem if the auxiliary data is taken away (as done by the last patch).
However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems. But then the work function must itself release the
work_struct by calling work_release().
In most cases, automatic release is fine, so this is the default. Special
initiators exist for the non-auto-release case (ending in _NAR).
Signed-Off-By: David Howells <dhowells@redhat.com>
Remove the now-unneeded kthread_stop_sem().
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move kthread API kernel-doc from kthread.h to kthread.c & fix it.
Add kthread API to kernel-api DocBook.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
A couple of places are forgetting to take it.
The kswapd case is probably unimportant. keventd_create_kthread() was racy.
The whole thing is a bit flakey: you start a kernel thread, get its pid from
kernel_thread() then look up its task_struct.
a) It assumes that pid recycling takes a "long" time.
b) We get a task_struct but no reference was taken on it. The owner of the
kswapd and kthread task_struct*'s must assume that the new thread won't
exit unexpectedly. Because if it does, they're left holding dead memory
and any attempt to control or stop that task will crash.
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Semaphore to mutex conversion.
The conversion was generated via scripts, and the result was validated
automatically via a script as well.
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Enhance the kthread API by adding kthread_stop_sem, for use in stopping
threads that spend their idle time waiting on a semaphore.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Replace a number of memory barriers with smp_ variants. This means we won't
take the unnecessary hit on UP machines.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
