Masami Hiramatsu d8bb6718c4 arm64: Make debug exception handlers visible from RCU ... Make debug exceptions visible from RCU so that synchronize_rcu() correctly track the debug exception handler. This also introduces sanity checks for user-mode exceptions as same as x86's ist_enter()/ist_exit(). The debug exception can interrupt in idle task. For example, it warns if we put a kprobe on a function called from idle task as below. The warning message showed that the rcu_read_lock() caused this problem. But actually, this means the RCU is lost the context which is already in NMI/IRQ. /sys/kernel/debug/tracing # echo p default_idle_call >> kprobe_events /sys/kernel/debug/tracing # echo 1 > events/kprobes/enable /sys/kernel/debug/tracing # [ 135.122237] [ 135.125035] ============================= [ 135.125310] WARNING: suspicious RCU usage [ 135.125581] 5.2.0-08445-g9187c508bdc7 #20 Not tainted [ 135.125904] ----------------------------- [ 135.126205] include/linux/rcupdate.h:594 rcu_read_lock() used illegally while idle! [ 135.126839] [ 135.126839] other info that might help us debug this: [ 135.126839] [ 135.127410] [ 135.127410] RCU used illegally from idle CPU! [ 135.127410] rcu_scheduler_active = 2, debug_locks = 1 [ 135.128114] RCU used illegally from extended quiescent state! [ 135.128555] 1 lock held by swapper/0/0: [ 135.128944] #0: (____ptrval____) (rcu_read_lock){....}, at: call_break_hook+0x0/0x178 [ 135.130499] [ 135.130499] stack backtrace: [ 135.131192] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-08445-g9187c508bdc7 #20 [ 135.131841] Hardware name: linux,dummy-virt (DT) [ 135.132224] Call trace: [ 135.132491] dump_backtrace+0x0/0x140 [ 135.132806] show_stack+0x24/0x30 [ 135.133133] dump_stack+0xc4/0x10c [ 135.133726] lockdep_rcu_suspicious+0xf8/0x108 [ 135.134171] call_break_hook+0x170/0x178 [ 135.134486] brk_handler+0x28/0x68 [ 135.134792] do_debug_exception+0x90/0x150 [ 135.135051] el1_dbg+0x18/0x8c [ 135.135260] default_idle_call+0x0/0x44 [ 135.135516] cpu_startup_entry+0x2c/0x30 [ 135.135815] rest_init+0x1b0/0x280 [ 135.136044] arch_call_rest_init+0x14/0x1c [ 135.136305] start_kernel+0x4d4/0x500 [ 135.136597] So make debug exception visible to RCU can fix this warning. Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Will Deacon <will@kernel.org>		2019-08-02 11:56:01 +01:00
..
cache.S	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
context.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
copypage.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
dma-mapping.c	IOMMU Updates for Linux v5.3	2019-07-09 09:21:02 -07:00
dump.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441	2019-06-05 17:37:17 +02:00
extable.c
fault.c	arm64: Make debug exception handlers visible from RCU	2019-08-02 11:56:01 +01:00
flush.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
hugetlbpage.c	arm64/hugetlb: Use macros for contiguous huge page sizes	2019-06-03 16:58:37 +01:00
init.c	arm64 updates for 5.3:	2019-07-08 09:54:55 -07:00
ioremap.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
kasan_init.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500	2019-06-19 17:09:55 +02:00
Makefile
mmap.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
mmu.c	mm/memory_hotplug: allow arch_remove_memory() without CONFIG_MEMORY_HOTREMOVE	2019-07-18 17:08:06 -07:00
numa.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
pageattr.c	mm/pgtable: drop pgtable_t variable from pte_fn_t functions	2019-07-12 11:05:46 -07:00
pgd.c	arm64: switch to generic version of pte allocation	2019-07-12 11:05:45 -07:00
physaddr.c
proc.S	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234	2019-06-19 17:09:07 +02:00
ptdump_debugfs.c	arm64: dump: no need to check return value of debugfs_create functions	2019-01-31 17:38:19 +00:00