FAILED: Patch "posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone" failed to apply to v5.4-stable tree
Subsystems (5)
Sasha Levin
maintainerThe patch below does not apply to the v5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
From b5413156bad91dc2995a5c4eab1b05e56914638a Mon Sep 17 00:00:00 2001
From: Benjamin Segall <[email protected]>
Date: Fri, 25 Oct 2024 18:35:35 -0700
Subject: [PATCH] posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone
When cloning a new thread, its posix_cputimers are not inherited, and are cleared by posix_cputimers_init(). However, this does not clear the tick dependency it creates in tsk->tick_dep_mask, and the handler does not reach the code to clear the dependency if there were no timers to begin with.
Thus if a thread has a cputimer running before clone/fork, all descendants will prevent nohz_full unless they create a cputimer of their own.
Fix this by entirely clearing the tick_dep_mask in copy_process(). (There is currently no inherited state that needs a tick dependency)
Process-wide timers do not have this problem because fork does not copy signal_struct as a baseline, it creates one from scratch.
--- include/linux/tick.h | 8 ++++++++ kernel/fork.c | 2 ++ 2 files changed, 10 insertions(+)
include/linux/tick.h +8 -0
@@ -251,12 +251,19 @@ static inline void tick_dep_set_task(struct task_struct *tsk,if (tick_nohz_full_enabled ())tick_nohz_dep_set_task (tsk, bit); } +static inline void tick_dep_clear_task (struct task_struct *tsk,enum tick_dep_bits bit) {if (tick_nohz_full_enabled ())tick_nohz_dep_clear_task (tsk, bit); } + +static inline void tick_dep_init_task (struct task_struct *tsk) +{ +atomic_set (&tsk->tick_dep_mask,0 ); +} +static inline void tick_dep_set_signal (struct task_struct *tsk,enum tick_dep_bits bit) {
@@ -290,6 +297,7 @@ static inline void tick_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) { }static inline void tick_dep_clear_task (struct task_struct *tsk,enum tick_dep_bits bit) { } +static inline void tick_dep_init_task (struct task_struct *tsk) { }static inline void tick_dep_set_signal (struct task_struct *tsk,enum tick_dep_bits bit) { } static inline void tick_dep_clear_signal(struct signal_struct *signal,
kernel/fork.c +2 -0
@@ -105,6 +105,7 @@#include <linux/rseq.h> #include <uapi/linux/pidfd.h> #include <linux/pidfs.h> +#include <linux/tick.h> #include <asm/pgalloc.h> #include <linux/uaccess.h>
@@ -2292,6 +2293,7 @@ __latent_entropy struct task_struct *copy_process(acct_clear_integrals (p);posix_cputimers_init (&p->posix_cputimers); +tick_dep_init_task (p); p->io_context =NULL ;audit_set_context (p,NULL );
Signature · 1 line
2.43.0
Quoted 7 lines · Sasha Levin
The patch below does not apply to the v5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.Thanks,
Sasha
Please try this:
From 6b742b3fa045260c3b13e7747332e9d34ca7bbe9 Mon Sep 17 00:00:00 2001
From: Benjamin Segall <[email protected]>
Date: Fri, 25 Oct 2024 18:35:35 -0700
Subject: [PATCH] posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone
When cloning a new thread, its posix_cputimers are not inherited, and are cleared by posix_cputimers_init(). However, this does not clear the tick dependency it creates in tsk->tick_dep_mask, and the handler does not reach the code to clear the dependency if there were no timers to begin with.
Thus if a thread has a cputimer running before clone/fork, all descendants will prevent nohz_full unless they create a cputimer of their own.
Fix this by entirely clearing the tick_dep_mask in copy_process(). (There is currently no inherited state that needs a tick dependency)
Process-wide timers do not have this problem because fork does not copy signal_struct as a baseline, it creates one from scratch.
--- include/linux/tick.h | 8 ++++++++ kernel/fork.c | 2 ++ 2 files changed, 10 insertions(+)
include/linux/tick.h +8 -0
@@ -244,12 +244,19 @@ static inline void tick_dep_set_task(struct task_struct *tsk,if (tick_nohz_full_enabled ())tick_nohz_dep_set_task (tsk, bit); } +static inline void tick_dep_clear_task (struct task_struct *tsk,enum tick_dep_bits bit) {if (tick_nohz_full_enabled ())tick_nohz_dep_clear_task (tsk, bit); } + +static inline void tick_dep_init_task (struct task_struct *tsk) +{ +atomic_set (&tsk->tick_dep_mask,0 ); +} +static inline void tick_dep_set_signal (struct signal_struct *signal,enum tick_dep_bits bit) {
@@ -283,6 +290,7 @@ static inline void tick_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) { }static inline void tick_dep_clear_task (struct task_struct *tsk,enum tick_dep_bits bit) { } +static inline void tick_dep_init_task (struct task_struct *tsk) { }static inline void tick_dep_set_signal (struct signal_struct *signal,enum tick_dep_bits bit) { } static inline void tick_dep_clear_signal(struct signal_struct *signal,
kernel/fork.c +2 -0
@@ -94,6 +94,7 @@#include <linux/livepatch.h> #include <linux/thread_info.h> #include <linux/stackleak.h> +#include <linux/tick.h> #include <asm/pgtable.h> #include <asm/pgalloc.h>
@@ -1956,6 +1957,7 @@ static __latent_entropy struct task_struct *copy_process(acct_clear_integrals (p);posix_cputimers_init (&p->posix_cputimers); +tick_dep_init_task (p); p->io_context =NULL ;audit_set_context (p,NULL );
Signature · 1 line
2.46.0