2021-03-17 10:23:53

by Eugeniu Rosca

Subject: [PATCH v2] softirq: s/BUG/WARN_ONCE/ on tasklet SCHED state not set

From: Dirk Behme <[email protected]>

Replace BUG() with WARN_ONCE() on wrong tasklet state, in order to:
* increase the verbosity / aid in debugging
* avoid fatal/unrecoverable state

Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Dirk Behme <[email protected]>
Signed-off-by: Eugeniu Rosca <[email protected]>
---

Changes since v1:
* Factored out the change into a separate function
* Replaced BUG with WARN_ONCE
* Fixed 'checkpatch --strict' errors
* v1: https://lore.kernel.org/lkml/[email protected]/

kernel/softirq.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9908ec4a9bfe..17a93d47b9a1 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -531,6 +531,18 @@ void __tasklet_hi_schedule(struct tasklet_struct *t)
}
EXPORT_SYMBOL(__tasklet_hi_schedule);

+static bool tasklet_should_run(struct tasklet_struct *t)
+{
+ if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
+ return true;
+
+ WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
+ t->use_callback ? "callback" : "func",
+ t->use_callback ? (void *)t->callback : (void *)t->func);
+
+ return false;
+}
+
static void tasklet_action_common(struct softirq_action *a,
struct tasklet_head *tl_head,
unsigned int softirq_nr)
@@ -550,13 +562,12 @@ static void tasklet_action_common(struct softirq_action *a,

if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
- if (!test_and_clear_bit(TASKLET_STATE_SCHED,
- &t->state))
- BUG();
- if (t->use_callback)
- t->callback(t);
- else
- t->func(t->data);
+ if (tasklet_should_run(t)) {
+ if (t->use_callback)
+ t->callback(t);
+ else
+ t->func(t->data);
+ }
tasklet_unlock(t);
continue;
}
--
2.29.0

2021-03-17 17:05:26

by tip-bot2 for Jacob Pan

Subject: [tip: irq/core] softirq: s/BUG/WARN_ONCE/ on tasklet SCHED state not set

The following commit has been merged into the irq/core branch of tip:

Commit-ID: 6b2c339df90788ce6aeecee78d6494f262929206
Gitweb: https://git.kernel.org/tip/6b2c339df90788ce6aeecee78d6494f262929206
Author: Dirk Behme <[email protected]>
AuthorDate: Wed, 17 Mar 2021 11:20:12 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Wed, 17 Mar 2021 12:59:35 +01:00

softirq: s/BUG/WARN_ONCE/ on tasklet SCHED state not set

Replace BUG() with WARN_ONCE() on wrong tasklet state, in order to:

- increase the verbosity / aid in debugging
- avoid fatal/unrecoverable state

Suggested-by: Thomas Gleixner <[email protected]>
Signed-off-by: Dirk Behme <[email protected]>
Signed-off-by: Eugeniu Rosca <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/softirq.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8b44ab9..8d56bbf 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -531,6 +531,18 @@ void __tasklet_hi_schedule(struct tasklet_struct *t)
}
EXPORT_SYMBOL(__tasklet_hi_schedule);

+static bool tasklet_should_run(struct tasklet_struct *t)
+{
+ if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
+ return true;
+
+ WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
+ t->use_callback ? "callback" : "func",
+ t->use_callback ? (void *)t->callback : (void *)t->func);
+
+ return false;
+}
+
static void tasklet_action_common(struct softirq_action *a,
struct tasklet_head *tl_head,
unsigned int softirq_nr)
@@ -550,13 +562,12 @@ static void tasklet_action_common(struct softirq_action *a,

if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
- if (!test_and_clear_bit(TASKLET_STATE_SCHED,
- &t->state))
- BUG();
- if (t->use_callback)
- t->callback(t);
- else
- t->func(t->data);
+ if (tasklet_should_run(t)) {
+ if (t->use_callback)
+ t->callback(t);
+ else
+ t->func(t->data);
+ }
tasklet_unlock(t);
continue;
}