The patch titled
Subject: softirq: fix tasklet_kill() and its users
has been added to the -mm tree. Its filename is
softirq-fix-tasklet_kill-and-its-users.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/softirq-fix-tasklet_kill-and-its-users.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/softirq-fix-tasklet_kill-and-its-users.patch
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------------------------------------------------------
From: Santosh Shilimkar <ssantosh@xxxxxxxxxx>
Subject: softirq: fix tasklet_kill() and its users
Semantically the expectation from the tasklet init/kill API should be as
below.
tasklet_init() == Init and Enable scheduling
tasklet_kill() == Disable scheduling and Destroy
The tasklet_init() API exibits the above behavior but tasklet_kill() does
not. The tasklet handler can still get scheduled and run even after
tasklet_kill().
There are 2, 3 places where drivers are working around this issue by
calling tasklet_disable() which will add a usecount and thereby preventing
the handlers from being called.
tasklet_enable/tasklet_disable is a pair API and they are expected to be
used together. Usage of tasklet_disable() *just* to work around tasklet
scheduling after a kill is probably not the correct and intended use of
the API. We also happen to see similar issues where in the shutdown path
the tasklet_handler is getting called even after the tasklet_kill().
We fix this by ensuring that tasklet_kill() does the right thing and
thereby ensures that the tasklet handler won't run after tasklet_kil()
with a very simple change. The patch fixes the tasklet code and also
removes a few driver workarounds.
Link: http://lkml.kernel.org/r/1472089950-2724-1-git-send-email-ssantosh@xxxxxxxxxx
Signed-off-by: Santosh Shilimkar <ssantosh@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Paul Bolle <pebolle@xxxxxxxxxx>
Cc: Giovanni Cabiddu <giovanni.cabiddu@xxxxxxxxx>
Cc: Salvatore Benedetto <salvatore.benedetto@xxxxxxxxx>
Cc: Karsten Keil <isdn@xxxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/crypto/qat/qat_common/adf_isr.c | 1 -
drivers/crypto/qat/qat_common/adf_sriov.c | 1 -
drivers/crypto/qat/qat_common/adf_vf_isr.c | 2 --
drivers/isdn/gigaset/interface.c | 1 -
kernel/softirq.c | 7 ++++---
5 files changed, 4 insertions(+), 8 deletions(-)
diff -puN drivers/crypto/qat/qat_common/adf_isr.c~softirq-fix-tasklet_kill-and-its-users drivers/crypto/qat/qat_common/adf_isr.c
--- a/drivers/crypto/qat/qat_common/adf_isr.c~softirq-fix-tasklet_kill-and-its-users
+++ a/drivers/crypto/qat/qat_common/adf_isr.c
@@ -296,7 +296,6 @@ static void adf_cleanup_bh(struct adf_ac
int i;
for (i = 0; i < hw_data->num_banks; i++) {
- tasklet_disable(&priv_data->banks[i].resp_handler);
tasklet_kill(&priv_data->banks[i].resp_handler);
}
}
diff -puN drivers/crypto/qat/qat_common/adf_sriov.c~softirq-fix-tasklet_kill-and-its-users drivers/crypto/qat/qat_common/adf_sriov.c
--- a/drivers/crypto/qat/qat_common/adf_sriov.c~softirq-fix-tasklet_kill-and-its-users
+++ a/drivers/crypto/qat/qat_common/adf_sriov.c
@@ -204,7 +204,6 @@ void adf_disable_sriov(struct adf_accel_
}
for (i = 0, vf = accel_dev->pf.vf_info; i < totalvfs; i++, vf++) {
- tasklet_disable(&vf->vf2pf_bh_tasklet);
tasklet_kill(&vf->vf2pf_bh_tasklet);
mutex_destroy(&vf->pf2vf_lock);
}
diff -puN drivers/crypto/qat/qat_common/adf_vf_isr.c~softirq-fix-tasklet_kill-and-its-users drivers/crypto/qat/qat_common/adf_vf_isr.c
--- a/drivers/crypto/qat/qat_common/adf_vf_isr.c~softirq-fix-tasklet_kill-and-its-users
+++ a/drivers/crypto/qat/qat_common/adf_vf_isr.c
@@ -191,7 +191,6 @@ static int adf_setup_pf2vf_bh(struct adf
static void adf_cleanup_pf2vf_bh(struct adf_accel_dev *accel_dev)
{
- tasklet_disable(&accel_dev->vf.pf2vf_bh_tasklet);
tasklet_kill(&accel_dev->vf.pf2vf_bh_tasklet);
mutex_destroy(&accel_dev->vf.vf2pf_lock);
}
@@ -268,7 +267,6 @@ static void adf_cleanup_bh(struct adf_ac
{
struct adf_etr_data *priv_data = accel_dev->transport;
- tasklet_disable(&priv_data->banks[0].resp_handler);
tasklet_kill(&priv_data->banks[0].resp_handler);
}
diff -puN drivers/isdn/gigaset/interface.c~softirq-fix-tasklet_kill-and-its-users drivers/isdn/gigaset/interface.c
--- a/drivers/isdn/gigaset/interface.c~softirq-fix-tasklet_kill-and-its-users
+++ a/drivers/isdn/gigaset/interface.c
@@ -524,7 +524,6 @@ void gigaset_if_free(struct cardstate *c
if (!drv->have_tty)
return;
- tasklet_disable(&cs->if_wake_tasklet);
tasklet_kill(&cs->if_wake_tasklet);
cs->tty_dev = NULL;
tty_unregister_device(drv->tty, cs->minor_index);
diff -puN kernel/softirq.c~softirq-fix-tasklet_kill-and-its-users kernel/softirq.c
--- a/kernel/softirq.c~softirq-fix-tasklet_kill-and-its-users
+++ a/kernel/softirq.c
@@ -498,7 +498,7 @@ static void tasklet_action(struct softir
list = list->next;
if (tasklet_trylock(t)) {
- if (!atomic_read(&t->count)) {
+ if (atomic_read(&t->count) == 1) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED,
&t->state))
BUG();
@@ -534,7 +534,7 @@ static void tasklet_hi_action(struct sof
list = list->next;
if (tasklet_trylock(t)) {
- if (!atomic_read(&t->count)) {
+ if (atomic_read(&t->count) == 1) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED,
&t->state))
BUG();
@@ -559,7 +559,7 @@ void tasklet_init(struct tasklet_struct
{
t->next = NULL;
t->state = 0;
- atomic_set(&t->count, 0);
+ atomic_set(&t->count, 1);
t->func = func;
t->data = data;
}
@@ -576,6 +576,7 @@ void tasklet_kill(struct tasklet_struct
} while (test_bit(TASKLET_STATE_SCHED, &t->state));
}
tasklet_unlock_wait(t);
+ atomic_dec(&t->count);
clear_bit(TASKLET_STATE_SCHED, &t->state);
}
EXPORT_SYMBOL(tasklet_kill);
_
Patches currently in -mm which might be from ssantosh@xxxxxxxxxx are
softirq-fix-tasklet_kill-and-its-users.patch
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