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Message-ID: <173002230033.1442.372126072824359559.tip-bot2@tip-bot2>
Date: Sun, 27 Oct 2024 09:45:00 -0000
From: "tip-bot2 for Benjamin Segall" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Ben Segall <bsegall@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>, stable@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: timers/urgent] posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER
on clone
The following commit has been merged into the timers/urgent branch of tip:
Commit-ID: b5413156bad91dc2995a5c4eab1b05e56914638a
Gitweb: https://git.kernel.org/tip/b5413156bad91dc2995a5c4eab1b05e56914638a
Author: Benjamin Segall <bsegall@...gle.com>
AuthorDate: Fri, 25 Oct 2024 18:35:35 -07:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Sun, 27 Oct 2024 10:36:04 +01:00
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.
Fixes: b78783000d5c ("posix-cpu-timers: Migrate to use new tick dependency mask model")
Signed-off-by: Ben Segall <bsegall@...gle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/xm26o737bq8o.fsf@google.com
---
include/linux/tick.h | 8 ++++++++
kernel/fork.c | 2 ++
2 files changed, 10 insertions(+)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 7274463..99c9c5a 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -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,
diff --git a/kernel/fork.c b/kernel/fork.c
index 89ceb4a..6fa9fe6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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);
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