pm24.git/kernel, branch v6.11-rc2

profiling: remove profile=sleep support

2024-08-04T20:36:28Z

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 Signed-off-by: Linus Torvalds

Merge tag 'timers-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-08-04T15:50:16Z

Pull timer fixes from Thomas Gleixner: "Two fixes for the timer/clocksource code: - The recent fix to make the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed in testing as some compilers hoist the access into the non-preemotible section where the pointer is actually used, but obviously compilers can rightfully invoke it where the code put it. Move it into the non-preemptible section right to the actual usage side to cure it. - The clocksource watchdog is supposed to emit a warning when the retry count is greater than one and the number of retries reaches the limit. The condition is backwards and warns always when the count is greater than one. Fixup the condition to prevent spamming dmesg" * tag 'timers-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: clocksource: Fix brown-bag boolean thinko in cs_watchdog_read() tick/broadcast: Move per CPU pointer access into the atomic section

Merge tag 'sched-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-08-04T15:46:14Z

Pull scheduler fixes from Thomas Gleixner: - When stime is larger than rtime due to accounting imprecision, then utime = rtime - stime becomes negative. As this is unsigned math, the result becomes a huge positive number. Cure it by resetting stime to rtime in that case, so utime becomes 0. - Restore consistent state when sched_cpu_deactivate() fails. When offlining a CPU fails in sched_cpu_deactivate() after the SMT present counter has been decremented, then the function aborts but fails to increment the SMT present counter and leaves it imbalanced. Consecutive operations cause it to underflow. Add the missing fixup for the error path. For SMT accounting the runqueue needs to marked online again in the error exit path to restore consistent state. * tag 'sched-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/core: Fix unbalance set_rq_online/offline() in sched_cpu_deactivate() sched/core: Introduce sched_set_rq_on/offline() helper sched/smt: Fix unbalance sched_smt_present dec/inc sched/smt: Introduce sched_smt_present_inc/dec() helper sched/cputime: Fix mul_u64_u64_div_u64() precision for cputime

Merge tag 'locking-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-08-04T15:32:31Z

Pull locking fixes from Thomas Gleixner: "Two fixes for locking and jump labels: - Ensure that the atomic_cmpxchg() conditions are correct and evaluating to true on any non-zero value except 1. The missing check of the return value leads to inconsisted state of the jump label counter. - Add a missing type conversion in the paravirt spinlock code which makes loongson build again" * tag 'locking-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: jump_label: Fix the fix, brown paper bags galore locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

clocksource: Fix brown-bag boolean thinko in cs_watchdog_read()

2024-08-02T16:29:28Z

The current "nretries > 1 || nretries >= max_retries" check in cs_watchdog_read() will always evaluate to true, and thus pr_warn(), if nretries is greater than 1. The intent is instead to never warn on the first try, but otherwise warn if the successful retry was the last retry. Therefore, change that "||" to "&&". Fixes: db3a34e17433 ("clocksource: Retry clock read if long delays detected") Reported-by: Borislav Petkov Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20240802154618.4149953-2-paulmck@kernel.org

jump_label: Fix the fix, brown paper bags galore

2024-07-31T10:57:39Z

Per the example of: !atomic_cmpxchg(&key->enabled, 0, 1) the inverse was written as: atomic_cmpxchg(&key->enabled, 1, 0) except of course, that while !old is only true for old == 0, old is true for everything except old == 0. Fix it to read: atomic_cmpxchg(&key->enabled, 1, 0) == 1 such that only the 1->0 transition returns true and goes on to disable the keys. Fixes: 83ab38ef0a0b ("jump_label: Fix concurrency issues in static_key_slow_dec()") Reported-by: Darrick J. Wong Signed-off-by: Peter Zijlstra (Intel) Tested-by: Darrick J. Wong Link: https://lkml.kernel.org/r/20240731105557.GY33588@noisy.programming.kicks-ass.net

tick/broadcast: Move per CPU pointer access into the atomic section

2024-07-31T10:37:43Z

The recent fix for making the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed as compilers hoist the access into the non-preemptible region where the pointer is actually used. But of course it's valid that the compiler keeps it at the place where the code puts it which rightfully triggers: BUG: using smp_processor_id() in preemptible [00000000] code: caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0 Move it to the actual usage site which is in a non-preemptible region. Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable") Reported-by: David Wang <00107082@163.com> Signed-off-by: Thomas Gleixner Tested-by: Yu Liao Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx

profiling: remove stale percpu flip buffer variables

2024-07-29T23:34:17Z

For some reason I didn't see this issue on my arm64 or x86-64 builds, but Stephen Rothwell reports that commit 2accfdb7eff6 ("profiling: attempt to remove per-cpu profile flip buffer") left these static variables around, and the powerpc build is unhappy about them: kernel/profile.c:52:28: warning: 'cpu_profile_flip' defined but not used [-Wunused-variable] 52 | static DEFINE_PER_CPU(int, cpu_profile_flip); | ^~~~~~~~~~~~~~~~ .. So remove these stale left-over remnants too. Fixes: 2accfdb7eff6 ("profiling: attempt to remove per-cpu profile flip buffer") Reported-by: Stephen Rothwell Signed-off-by: Linus Torvalds

task_work: make TWA_NMI_CURRENT handling conditional on IRQ_WORK

2024-07-29T19:05:06Z

The TWA_NMI_CURRENT handling very much depends on IRQ_WORK, but that isn't universally enabled everywhere. Maybe the IRQ_WORK infrastructure should just be unconditional - x86 ends up indirectly enabling it through unconditionally enabling PERF_EVENTS, for example. But it also gets enabled by having SMP support, or even if you just have PRINTK enabled. But in the meantime TWA_NMI_CURRENT causes tons of build failures on various odd minimal configs. Which did show up in linux-next, but despite that nobody bothered to fix it or even inform me until -rc1 was out. Fixes: 466e4d801cd4 ("task_work: Add TWA_NMI_CURRENT as an additional notify mode") Reported-by: Naresh Kamboju Reported-by: kernelci.org bot Reported-by: Guenter Roeck Cc: Peter Zijlstra Cc: Sebastian Andrzej Siewior Signed-off-by: Linus Torvalds

profiling: attempt to remove per-cpu profile flip buffer

2024-07-29T17:58:28Z

This is the really old legacy kernel profiling code, which has long since been obviated by "real profiling" (ie 'prof' and company), and mainly remains as a source of syzbot reports. There are anecdotal reports that people still use it for boot-time profiling, but it's unlikely that such use would care about the old NUMA optimizations in this code from 2004 (commit ad02973d42: "profile: 512x Altix timer interrupt livelock fix" in the BK import archive at [1]) So in order to head off future syzbot reports, let's try to simplify this code and get rid of the per-cpu profile buffers that are quite a large portion of the complexity footprint of this thing (including CPU hotplug callbacks etc). It's unlikely anybody will actually notice, or possibly, as Thomas put it: "Only people who indulge in nostalgia will notice :)". That said, if it turns out that this code is actually actively used by somebody, we can always revert this removal. Thus the "attempt" in the summary line. [ Note: in a small nod to "the profiling code can cause NUMA problems", this also removes the "increment the last entry in the profiling array on any unknown hits" logic. That would account any program counter in a module to that single counter location, and might exacerbate any NUMA cacheline bouncing issues ] Link: https://lore.kernel.org/all/CAHk-=wgs52BxT4Zjmjz8aNvHWKxf5_ThBY4bYL1Y6CTaNL2dTw@mail.gmail.com/ Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git [1] Cc: Thomas Gleixner Cc: Tetsuo Handa Signed-off-by: Linus Torvalds