Commit Graph

12 Commits

Author SHA1 Message Date
Paul E. McKenney
cdc694b235 rcu: Add kernel parameter to dump trace after RCU CPU stall warning
This commit adds a rcu_cpu_stall_ftrace_dump kernel boot parameter, that,
when set, causes the trace buffer to be dumped after an RCU CPU stall
warning is printed.  This kernel boot parameter is disabled by default,
maintaining compatibility with previous behavior.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-01 14:05:51 -07:00
Neeraj Upadhyay
3ae976a7e3 rcu: Correctly unlock root node in rcu_check_gp_start_stall()
On systems whose rcu_node tree has only one node, the
rcu_check_gp_start_stall() function's values of rnp and rnp_root will
be identical.  In this case, it clearly does not make sense to release
both rnp->lock and rnp_root->lock, but that is exactly what this function
does in the last early exit.  This commit therefore unlocks only rnp->lock
when rnp and rnp_root are equal.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:02:57 -07:00
Neeraj Upadhyay
6c70e9cd5f rcu: Fix nohz status in stall warning
The Documentation/RCU/stallwarn.txt file says that stall warnings
print "D" if dyntick-idle processing is enabled, but the code in
print_cpu_stall_fast_no_hz() prints "." instead.  This commit therefore
reverses the sense of the test to make the code match the documentation.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:00 -07:00
Paul E. McKenney
b51bcbbf16 rcu: Move forward-progress checkers into tree_stall.h
This commit further consolidates stall-warning functionality by moving
forward-progress checkers into kernel/rcu/tree_stall.h, updating a
comment or two while in the area.  More specifically, this commit moves
show_rcu_gp_kthreads(), rcu_check_gp_start_stall(), rcu_fwd_progress_check(),
sysrq_rcu, sysrq_show_rcu(), sysrq_rcudump_op, and rcu_sysrq_init() from
kernel/rcu/tree.c to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
7ac1907c9e rcu: Move irq-disabled stall-warning checking to tree_stall.h
The rcu_iw_handler() function's sole purpose in life is to indicate
whether a stalled CPU had interrupts disabled, so it belongs in
kernel/rcu/tree_stall.h.  This commit therefore makes that move,
clarifying its header comment while in the area.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
e23344c2ca rcu: Organize functions in tree_stall.h
This commit does only code movement, removal of now-unneeded forward
declarations, and addition of comments.  It organizes the functions
that implement RCU CPU stall warnings for normal grace periods into
three categories:

1.	Control of RCU CPU stall warnings, including computing timeouts.

2.	Interaction of stall warnings with grace periods.

3.	Actual printing of the RCU CPU stall-warning messages.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
59b73a2768 rcu: Move FAST_NO_HZ stall-warning code to tree_stall.h
This commit further consolidates the stall-warning code by moving
print_cpu_stall_info() and its helper functions along with
zero_cpu_stall_ticks() to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
40e69ac7d0 rcu: Inline RCU stall-warning info helper functions
The print_cpu_stall_info_begin() and print_cpu_stall_info_end() print a
single character each onto the console, and are a holdover from a time
when RCU CPU stall warning messages could be abbreviated using a long-gone
Kconfig option.  This commit therefore adds these single characters to
already-printed strings in the calling functions, and then eliminates
both print_cpu_stall_info_begin() and print_cpu_stall_info_end().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
21d0d79ab0 rcu: Inline RCU task stall-warning helper functions
The rcu_print_detail_task_stall(), rcu_print_task_stall_begin(), and
rcu_print_task_stall_end() functions were defined to allow long-gone
Kconfig options to provide an abbreviated RCU CPU stall warning printout.
This commit saves a few lines of code by inlining them into their sole
callers.

While in the area, a useless call of rcu_print_detail_task_stall_rnp()
on the root rcu_node structure was eliminated.  If there is only one
rcu_node structure, its tasks get printed twice, but if there are more,
the root rcu_node structure is guaranteed to have an empty list of blocked
tasks, hence the uselessness.  (Long ago, root rcu_node structures with
non-empty ->blkd_tasks lists could happen, but no longer.)

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
32255d51b6 rcu: Move RCU CPU stall-warning code out of tree.c
This commit completes the process of consolidating the code for RCU CPU
stall warnings for normal grace periods by moving the remaining such
code from kernel/rcu/tree.c to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
3fc3d1709f rcu: Move RCU CPU stall-warning code out of tree_plugin.h
The RCU CPU stall-warning code for normal grace periods is currently
scattered across two files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired.  Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit continues this process by moving stall-warning code from
kernel/rcu/tree_plugin.c to a new kernel/rcu/tree_stall.h file.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney
10462d6f58 rcu: Move RCU CPU stall-warning code out of update.c
The RCU CPU stall-warning code for normal grace periods is currently
scattered across three files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired.  Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit starts this process by moving stall-warning code from
kernel/rcu/update.c to a new kernel/rcu/tree_stall.h file.

Note that the definitions of rcu_cpu_stall_suppress and
rcu_cpu_stall_timeout must remain in kernel/rcu/update.h to provide
compatibility for kernel boot parameter lists.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00