6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
commit b88f55389ad27f05ed84af9e1026aa64dbfabc9a upstream.
The kernel sleep profile is no longer working due to a recursive locking
bug introduced by commit 42a20f86dc19 ("sched: Add wrapper for get_wchan()
to keep task blocked")
Booting with the 'profile=sleep' kernel command line option added or
executing
# echo -n sleep > /sys/kernel/profiling
after boot causes the system to lock up.
Lockdep reports
kthreadd/3 is trying to acquire lock:
ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: get_wchan+0x32/0x70
but task is already holding lock:
ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: try_to_wake_up+0x53/0x370
with the call trace being
lock_acquire+0xc8/0x2f0
get_wchan+0x32/0x70
__update_stats_enqueue_sleeper+0x151/0x430
enqueue_entity+0x4b0/0x520
enqueue_task_fair+0x92/0x6b0
ttwu_do_activate+0x73/0x140
try_to_wake_up+0x213/0x370
swake_up_locked+0x20/0x50
complete+0x2f/0x40
kthread+0xfb/0x180
However, since nobody noticed this regression for more than two years,
let's remove 'profile=sleep' support based on the assumption that nobody
needs this functionality.
Fixes: 42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep task blocked")
Cc: stable@xxxxxxxxxxxxxxx # v5.16+
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 4 +---
include/linux/profile.h | 1 -
kernel/profile.c | 11 +----------
kernel/sched/stats.c | 10 ----------
4 files changed, 2 insertions(+), 24 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4655,11 +4655,9 @@
profile= [KNL] Enable kernel profiling via /proc/profile
Format: [<profiletype>,]<number>
- Param: <profiletype>: "schedule", "sleep", or "kvm"
+ Param: <profiletype>: "schedule" or "kvm"
[defaults to kernel profiling]
Param: "schedule" - profile schedule points.
- Param: "sleep" - profile D-state sleeping (millisecs).
- Requires CONFIG_SCHEDSTATS
Param: "kvm" - profile VM exits.
Param: <number> - step/bucket size as a power of 2 for
statistical time based profiling.
--- a/include/linux/profile.h
+++ b/include/linux/profile.h
@@ -11,7 +11,6 @@
#define CPU_PROFILING 1
#define SCHED_PROFILING 2
-#define SLEEP_PROFILING 3
#define KVM_PROFILING 4
struct proc_dir_entry;
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -57,20 +57,11 @@ static DEFINE_MUTEX(profile_flip_mutex);
int profile_setup(char *str)
{
static const char schedstr[] = "schedule";
- static const char sleepstr[] = "sleep";
static const char kvmstr[] = "kvm";
const char *select = NULL;
int par;
- if (!strncmp(str, sleepstr, strlen(sleepstr))) {
-#ifdef CONFIG_SCHEDSTATS
- force_schedstat_enabled();
- prof_on = SLEEP_PROFILING;
- select = sleepstr;
-#else
- pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
-#endif /* CONFIG_SCHEDSTATS */
- } else if (!strncmp(str, schedstr, strlen(schedstr))) {
+ if (!strncmp(str, schedstr, strlen(schedstr))) {
prof_on = SCHED_PROFILING;
select = schedstr;
} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -92,16 +92,6 @@ void __update_stats_enqueue_sleeper(stru
trace_sched_stat_blocked(p, delta);
- /*
- * Blocking time is in units of nanosecs, so shift by
- * 20 to get a milliseconds-range estimation of the
- * amount of time that the task spent sleeping:
- */
- if (unlikely(prof_on == SLEEP_PROFILING)) {
- profile_hits(SLEEP_PROFILING,
- (void *)get_wchan(p),
- delta >> 20);
- }
account_scheduler_latency(p, delta >> 10, 0);
}
}
