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rcu: Add running and boosted indications to RCU task stall dump

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Currently, rcu_print_task_stall() will dump out the PID, RCU reader
nesting level, the rcu_special structure's flags, and whether or not
that reader is on the ->blkd_tasks list.  When debugging RCU priority
boosting, it is also good to know whether the stalled RCU reader is
currently running and whether it is currently being RCU priority boosted.
This commit therefore adds this information to the output.

[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Apply feedback from Arnd Bergmann and kernel test robot. ]

Link: https://lore.kernel.org/all/20260925133922.1356404-1-arnd@kernel.org/
Link: https://lore.kernel.org/all/202609261005.GrnaXBXT-lkp@intel.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Reviewed-by: Kunwu Chan <kunwu.chan@gmail.com>
Tested-by: Kunwu Chan <kunwu.chan@gmail.com>
This commit is contained in:
Paul E. McKenney 2026-09-03 15:26:24 -07:00
parent e71035eb6e
commit 49be2ba9f0
2 changed files with 22 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/rcu/tree_plugin.h
View File

@ -11,8 +11,6 @@
* Paul E. McKenney <paulmck@linux.ibm.com>
*/
#include "../locking/rtmutex_common.h"
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
{
/*

24
kernel/rcu/tree_stall.h
View File

@ -11,6 +11,8 @@
#include <linux/kvm_para.h>
#include <linux/rcu_notifier.h>
#include <linux/smp.h>
#include <linux/rtmutex.h>
#include "../locking/rtmutex_common.h"
//////////////////////////////////////////////////////////////////////////////
//
@ -305,6 +307,8 @@ struct rcu_stall_chk_rdr {
int nesting;
union rcu_special rs;
bool on_blkd_list;
bool rcu_rdr_running;
int rcu_rdr_boosted;
};
/*
@ -313,6 +317,7 @@ struct rcu_stall_chk_rdr {
*/
static int check_slow_task(struct task_struct *t, void *arg)
{
struct rcu_node *rnp;
struct rcu_stall_chk_rdr *rscrp = arg;
if (task_curr(t))
@ -320,6 +325,19 @@ static int check_slow_task(struct task_struct *t, void *arg)
rscrp->nesting = t->rcu_read_lock_nesting;
rscrp->rs = t->rcu_read_unlock_special;
rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
rscrp->rcu_rdr_running = task_curr(t);
rscrp->rcu_rdr_boosted = 0;
if (rscrp->on_blkd_list) {
rnp = READ_ONCE(t->rcu_blocked_node);
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
if (rnp == READ_ONCE(t->rcu_blocked_node)) {
if (rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t)
rscrp->rcu_rdr_boosted = 1;
} else {
rscrp->rcu_rdr_boosted = 2;
}
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
}
return 0;
}
@ -357,12 +375,14 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
if (task_call_func(t, check_slow_task, &rscr))
pr_cont(" P%d", t->pid);
else
pr_cont(" P%d/%d:%c%c%c%c",
pr_cont(" P%d/%d:%c%c%c%c%c%c",
t->pid, rscr.nesting,
".b"[rscr.rs.b.blocked],
".q"[rscr.rs.b.need_qs],
".e"[rscr.rs.b.exp_hint],
".l"[rscr.on_blkd_list]);
".l"[rscr.on_blkd_list],
".R"[rscr.rcu_rdr_running],
".B?"[rscr.rcu_rdr_boosted]);
lockdep_assert_irqs_disabled();
put_task_struct(t);
ndetected++;