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  1. Mar 07, 2015
  3. Feb 12, 2015
    • Michal Hocko's avatar
      oom, PM: make OOM detection in the freezer path raceless · c32b3cbe
      Michal Hocko authored 
      

Commit 5695be14 ("OOM, PM: OOM killed task shouldn't escape PM
suspend") has left a race window when OOM killer manages to
note_oom_kill after freeze_processes checks the counter.  The race
window is quite small and really unlikely and partial solution deemed
sufficient at the time of submission.

Tejun wasn't happy about this partial solution though and insisted on a
full solution.  That requires the full OOM and freezer's task freezing
exclusion, though.  This is done by this patch which introduces oom_sem
RW lock and turns oom_killer_disable() into a full OOM barrier.

oom_killer_disabled check is moved from the allocation path to the OOM
level and we take oom_sem for reading for both the check and the whole
OOM invocation.

oom_killer_disable() takes oom_sem for writing so it waits for all
currently running OOM killer invocations.  Then it disable all the further
OOMs by setting oom_killer_disabled and checks for any oom victims.
Victims are counted via mark_tsk_oom_victim resp.  unmark_oom_victim.  The
last victim wakes up all waiters enqueued by oom_killer_disable().
Therefore this function acts as the full OOM barrier.

The page fault path is covered now as well although it was assumed to be
safe before.  As per Tejun, "We used to have freezing points deep in file
system code which may be reacheable from page fault." so it would be
better and more robust to not rely on freezing points here.  Same applies
to the memcg OOM killer.

out_of_memory tells the caller whether the OOM was allowed to trigger and
the callers are supposed to handle the situation.  The page allocation
path simply fails the allocation same as before.  The page fault path will
retry the fault (more on that later) and Sysrq OOM trigger will simply
complain to the log.

Normally there wouldn't be any unfrozen user tasks after
try_to_freeze_tasks so the function will not block. But if there was an
OOM killer racing with try_to_freeze_tasks and the OOM victim didn't
finish yet then we have to wait for it. This should complete in a finite
time, though, because

	- the victim cannot loop in the page fault handler (it would die
	  on the way out from the exception)
	- it cannot loop in the page allocator because all the further
	  allocation would fail and __GFP_NOFAIL allocations are not
	  acceptable at this stage
	- it shouldn't be blocked on any locks held by frozen tasks
	  (try_to_freeze expects lockless context) and kernel threads and
	  work queues are not frozen yet

Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Suggested-by: default avatarTejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c32b3cbe
    • Michal Hocko's avatar
      sysrq: convert printk to pr_* equivalent · 401e4a7c
      Michal Hocko authored 
      

While touching this area let's convert printk to pr_*.  This also makes
the printing of continuation lines done properly.

Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      401e4a7c
  5. Feb 07, 2015
  7. Feb 03, 2015
  9. Feb 02, 2015
    • Marek Szyprowski's avatar
      serial: samsung: earlycon support depends on CONFIG_SERIAL_SAMSUNG_CONSOLE · c3bda295
      Marek Szyprowski authored 
      

EarlyCon support depends on serial console infrastructure, so the code
implementing it should depend on CONFIG_SERIAL_SAMSUNG_CONSOLE.

This patch fixes the following build break:
CC [M]  drivers/tty/serial/samsung.o
drivers/tty/serial/samsung.c:2468:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2468:1: error: expected declaration specifiers or ‘...’ before ‘s3c2410_setup_earlycon’
drivers/tty/serial/samsung.c:2487:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2487:1: error: expected declaration specifiers or ‘...’ before ‘s3c2412_setup_earlycon’
drivers/tty/serial/samsung.c:2488:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2488:1: error: expected declaration specifiers or ‘...’ before ‘s3c2440_setup_earlycon’
drivers/tty/serial/samsung.c:2489:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2489:1: error: expected declaration specifiers or ‘...’ before ‘s3c6400_setup_earlycon’
drivers/tty/serial/samsung.c:2506:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2506:1: error: expected declaration specifiers or ‘...’ before ‘s5pv210_setup_earlycon’
drivers/tty/serial/samsung.c:2507:1: error: expected declaration specifiers or ‘...’ before string constant
drivers/tty/serial/samsung.c:2507:1: error: expected declaration specifiers or ‘...’ before ‘exynos4210_setup_earlycon’
drivers/tty/serial/samsung.c:2468:1: warning: ‘s3c2410_setup_earlycon’ defined but not used [-Wunused-function]
drivers/tty/serial/samsung.c:2487:1: warning: ‘s3c2412_setup_earlycon’ defined but not used [-Wunused-function]
drivers/tty/serial/samsung.c:2488:1: warning: ‘s3c2440_setup_earlycon’ defined but not used [-Wunused-function]
drivers/tty/serial/samsung.c:2489:1: warning: ‘s3c6400_setup_earlycon’ defined but not used [-Wunused-function]
drivers/tty/serial/samsung.c:2506:1: warning: ‘s5pv210_setup_earlycon’ defined but not used [-Wunused-function]
drivers/tty/serial/samsung.c:2507:1: warning: ‘exynos4210_setup_earlycon’ defined but not used [-Wunused-function]
make[3]: *** [drivers/tty/serial/samsung.o] Error 1

Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      c3bda295