Luis R. Rodriguez 165d1cc007 kmod: reduce atomic operations on kmod_concurrent and simplify ... When checking if we want to allow a kmod thread to kick off we increment, then read to see if we should enable a thread. If we were over the allowed limit limit we decrement. Splitting the increment far apart from decrement means there could be a time where two increments happen potentially giving a false failure on a thread which should have been allowed. CPU1 CPU2 atomic_inc() atomic_inc() atomic_read() atomic_read() atomic_dec() atomic_dec() In this case a read on CPU1 gets the atomic_inc()'s and we could negate it from getting a kmod thread. We could try to prevent this with a lock or preemption but that is overkill. We can fix by reducing the number of atomic operations. We do this by inverting the logic of of the enabler, instead of incrementing kmod_concurrent as we get new kmod users, define the variable kmod_concurrent_max as the max number of currently allowed kmod users and as we get new kmod users just decrement it if its still positive. This combines the dec and read in one atomic operation. In this case we no longer get the same false failure: CPU1 CPU2 atomic_dec_if_positive() atomic_dec_if_positive() atomic_inc() atomic_inc() The number of threads is computed at init, and since the current computation of kmod_concurrent includes the thread count we can avoid setting kmod_concurrent_max later in boot through an init call by simply sticking to 50 as the kmod_concurrent_max. The assumption here is a system with modules must at least have ~16 MiB of RAM. Suggested-by: Petr Mladek <pmladek@suse.com> Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Jessica Yu <jeyu@kernel.org>		2017-06-27 19:36:31 +02:00
..
bpf	bpf: adjust verifier heuristics	2017-05-17 22:55:27 -04:00
cgroup	Merge branch 'for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2017-05-01 13:52:24 -07:00
configs	config: android-base: enable hardened usercopy and kernel ASLR	2017-02-27 18:43:46 -08:00
debug	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
events	perf/callchain: Force USER_DS when invoking perf_callchain_user()	2017-05-10 07:54:00 +02:00
gcov	gcov: support GCC 7.1	2017-05-12 15:57:15 -07:00
irq	Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-21 11:45:26 -07:00
livepatch	Merge branches 'for-4.12/upstream' and 'for-4.12/klp-hybrid-consistency-model' into for-linus	2017-05-01 21:49:28 +02:00
locking	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
power	More power management updates for v4.12-rc1	2017-05-10 09:12:30 -07:00
printk	TTY/Serial patches for 4.12-rc1	2017-05-08 18:49:23 -07:00
rcu	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
sched	sched/core: Call __schedule() from do_idle() without enabling preemption	2017-05-15 10:09:12 +02:00
time	time: delete current_fs_time()	2017-05-12 15:57:15 -07:00
trace	This fixes a bug caused by not cleaning up the new instance unique triggers	2017-05-20 23:39:03 -07:00
.gitignore
acct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
async.c
audit.c	Merge branch 'stable-4.12' of git://git.infradead.org/users/pcmoore/audit	2017-05-03 09:21:59 -07:00
audit.h	audit: Use timespec64 to represent audit timestamps	2017-05-02 10:16:05 -04:00
audit_fsnotify.c	Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs	2017-05-03 11:05:15 -07:00
audit_tree.c	Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs	2017-05-03 11:05:15 -07:00
audit_watch.c	Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs	2017-05-03 11:05:15 -07:00
auditfilter.c	audit: kernel generated netlink traffic should have a portid of 0	2017-05-02 10:16:05 -04:00
auditsc.c	Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs	2017-05-03 11:05:15 -07:00
backtracetest.c
bounds.c
capability.c	capability: export has_capability	2017-01-12 07:01:56 -07:00
compat.c	time: Change k_clock nsleep() to use timespec64	2017-04-14 21:49:56 +02:00
configs.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
context_tracking.c
cpu.c	Merge branch 'linus' into locking/core, to pick up fixes	2017-04-14 10:29:40 +02:00
cpu_pm.c
crash_core.c	ia64: reuse append_elf_note() and final_note() functions	2017-05-08 17:15:11 -07:00
crash_dump.c
cred.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/coredump.h>	2017-03-02 08:42:28 +01:00
delayacct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c	userfaultfd: non-cooperative: rollback userfaultfd_exit	2017-03-09 17:01:09 -08:00
extable.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2017-02-22 10:15:09 -08:00
fork.c	pid_ns: Fix race between setns'ed fork() and zap_pid_ns_processes()	2017-05-13 17:26:02 -05:00
freezer.c
futex.c	futex: Clarify mark_wake_futex memory barrier usage	2017-04-15 16:03:46 +02:00
futex_compat.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
groups.c	mm, vmalloc: use __GFP_HIGHMEM implicitly	2017-05-08 17:15:13 -07:00
hung_task.c	kernel/hung_task.c: defer showing held locks	2017-05-08 17:15:10 -07:00
irq_work.c
jump_label.c	This release has no new tracing features, just clean ups, minor fixes	2017-02-27 13:26:17 -08:00
kallsyms.c	bpf: make jited programs visible in traces	2017-02-17 13:40:05 -05:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c	kcov: simplify interrupt check	2017-05-08 17:15:12 -07:00
kexec.c
kexec_core.c	ia64: reuse append_elf_note() and final_note() functions	2017-05-08 17:15:11 -07:00
kexec_file.c	kexec, x86/purgatory: Unbreak it and clean it up	2017-03-10 20:55:09 +01:00
kexec_internal.h	kexec, x86/purgatory: Unbreak it and clean it up	2017-03-10 20:55:09 +01:00
kmod.c	kmod: reduce atomic operations on kmod_concurrent and simplify	2017-06-27 19:36:31 +02:00
kprobes.c	kprobes: Document how optimized kprobes are removed from module unload	2017-05-17 21:55:58 -04:00
ksysfs.c	crash: move crashkernel parsing and vmcore related code under CONFIG_CRASH_CORE	2017-05-08 17:15:11 -07:00
kthread.c	cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups	2017-03-17 10:18:47 -04:00
latencytop.c	sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h>	2017-03-02 08:42:39 +01:00
Makefile	crash: move crashkernel parsing and vmcore related code under CONFIG_CRASH_CORE	2017-05-08 17:15:11 -07:00
membarrier.c	Fix: Disable sys_membarrier when nohz_full is enabled	2017-01-23 11:32:16 -08:00
memremap.c	mm, zone_device: Replace {get, put}_zone_device_page() with a single reference to fix pmem crash	2017-05-01 09:15:53 +02:00
module-internal.h
module.c	module: use list_for_each_entry_rcu() on find_module_all()	2017-06-27 19:35:52 +02:00
module_signing.c
notifier.c	kernel/notifier.c: simplify expression	2017-02-24 17:46:56 -08:00
nsproxy.c	perf: Add PERF_RECORD_NAMESPACES to include namespaces related info	2017-03-13 15:57:41 -03:00
padata.c	padata: get_next is never NULL	2017-04-21 20:30:46 +08:00
panic.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
params.c	boot/param: Move next_arg() function to lib/cmdline.c for later reuse	2017-04-18 10:37:13 +02:00
pid.c	pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid()	2017-05-08 17:15:12 -07:00
pid_namespace.c	pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes	2017-05-13 17:26:01 -05:00
profile.c	sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h>	2017-03-02 08:42:39 +01:00
ptrace.c	ptrace: fix PTRACE_LISTEN race corrupting task->state	2017-04-08 00:47:48 -07:00
range.c
reboot.c
relay.c	Merge branch 'work.splice' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2017-05-02 11:38:06 -07:00
resource.c
seccomp.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>	2017-03-02 08:42:36 +01:00
signal.c	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
smp.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/idle.h>	2017-03-02 08:42:26 +01:00
smpboot.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
smpboot.h
softirq.c	sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags()	2017-04-11 09:06:32 +02:00
stacktrace.c	stacktrace/x86: add function for detecting reliable stack traces	2017-03-08 09:18:02 +01:00
stop_machine.c
sys.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2017-05-05 11:08:43 -07:00
sys_ni.c	move aio compat to fs/aio.c	2016-12-22 22:58:37 -05:00
sysctl.c	proc/sysctl: fix the int overflow for jiffies conversion	2017-05-08 17:15:10 -07:00
sysctl_binary.c	net: Remove NET_CORE_BUDGET_USECS from sysctl binary interface.	2017-04-21 15:59:52 -04:00
task_work.c
taskstats.c	taskstats: add e/u/stime for TGID command	2017-05-08 17:15:12 -07:00
test_kprobes.c
torture.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h>	2017-03-02 08:42:27 +01:00
tracepoint.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
tsacct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
ucount.c	ucount: Remove the atomicity from ucount->count	2017-03-06 15:26:37 -06:00
uid16.c	sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h>	2017-03-02 08:42:31 +01:00
up.c
user-return-notifier.c
user.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h>	2017-03-02 08:42:29 +01:00
user_namespace.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h>	2017-03-02 08:42:29 +01:00
utsname.c	sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h>	2017-03-02 08:42:38 +01:00
utsname_sysctl.c	sched/headers: Remove <linux/rwsem.h> from <linux/sched.h>	2017-03-03 01:45:36 +01:00
watchdog.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
watchdog_hld.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
workqueue.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-01 19:12:53 -07:00
workqueue_internal.h