5.15-stable review patch. If anyone has any objections, please let me know.
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From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
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@vger.kernel.org # v5.16+ Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/admin-guide/kernel-parameters.txt | 4 +--- include/linux/profile.h | 1 - kernel/profile.c | 16 +--------------- kernel/sched/fair.c | 10 ---------- 4 files changed, 2 insertions(+), 29 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4355,11 +4355,9 @@
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 @@ -57,24 +57,10 @@ 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"; int par;
- if (!strncmp(str, sleepstr, strlen(sleepstr))) { -#ifdef CONFIG_SCHEDSTATS - force_schedstat_enabled(); - prof_on = SLEEP_PROFILING; - if (str[strlen(sleepstr)] == ',') - str += strlen(sleepstr) + 1; - if (get_option(&str, &par)) - prof_shift = clamp(par, 0, BITS_PER_LONG - 1); - pr_info("kernel sleep profiling enabled (shift: %u)\n", - prof_shift); -#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; if (str[strlen(schedstr)] == ',') str += strlen(schedstr) + 1; --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -988,16 +988,6 @@ update_stats_enqueue_sleeper(struct cfs_
trace_sched_stat_blocked(tsk, 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(tsk), - delta >> 20); - } account_scheduler_latency(tsk, delta >> 10, 0); } }