Thomas Gleixner 90e362f4a7 sched: Provide update_curr callbacks for stop/idle scheduling classes ... Chris bisected a NULL pointer deference in task_sched_runtime() to commit 6e998916df 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency'. Chris observed crashes in atop or other /proc walking programs when he started fork bombs on his machine. He assumed that this is a new exit race, but that does not make any sense when looking at that commit. What's interesting is that, the commit provides update_curr callbacks for all scheduling classes except stop_task and idle_task. While nothing can ever hit that via the clock_nanosleep() and clock_gettime() interfaces, which have been the target of the commit in question, the author obviously forgot that there are other code paths which invoke task_sched_runtime() do_task_stat(() thread_group_cputime_adjusted() thread_group_cputime() task_cputime() task_sched_runtime() if (task_current(rq, p) && task_on_rq_queued(p)) { update_rq_clock(rq); up->sched_class->update_curr(rq); } If the stats are read for a stomp machine task, aka 'migration/N' and that task is current on its cpu, this will happily call the NULL pointer of stop_task->update_curr. Ooops. Chris observation that this happens faster when he runs the fork bomb makes sense as the fork bomb will kick migration threads more often so the probability to hit the issue will increase. Add the missing update_curr callbacks to the scheduler classes stop_task and idle_task. While idle tasks cannot be monitored via /proc we have other means to hit the idle case. Fixes: 6e998916df 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency' Reported-by: Chris Mason <clm@fb.com> Reported-and-tested-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2014-11-23 14:14:40 -08:00
..
auto_group.c	sched: Change autogroup_move_group() to use for_each_thread()	2014-08-20 09:47:18 +02:00
auto_group.h
clock.c	time: Replace __get_cpu_var uses	2014-08-26 13:45:44 -04:00
completion.c
core.c	sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency	2014-11-16 10:04:20 +01:00
cpuacct.c
cpuacct.h
cpudeadline.c	sched/deadline: Fix inter- exclusive cpusets migrations	2014-09-24 14:46:57 +02:00
cpudeadline.h
cpupri.c
cpupri.h
cputime.c	sched, time: Fix build error with 64 bit cputime_t on 32 bit systems	2014-10-03 05:46:55 +02:00
deadline.c	sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency	2014-11-16 10:04:20 +01:00
debug.c	sched: print_rq(): Don't use tasklist_lock	2014-09-24 14:47:04 +02:00
fair.c	sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency	2014-11-16 10:04:20 +01:00
features.h
idle_task.c	sched: Provide update_curr callbacks for stop/idle scheduling classes	2014-11-23 14:14:40 -08:00
idle.c	sched: Let the scheduler see CPU idle states	2014-09-24 14:46:58 +02:00
Makefile
proc.c
rt.c	sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency	2014-11-16 10:04:20 +01:00
sched.h	sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency	2014-11-16 10:04:20 +01:00
stats.c
stats.h
stop_task.c	sched: Provide update_curr callbacks for stop/idle scheduling classes	2014-11-23 14:14:40 -08:00
wait.c	SCHED: add some "wait..on_bit...timeout()" interfaces.	2014-09-25 08:23:57 -04:00