When fixing the problem mentioned in PATCH1, we also found
the following problem:
If the IPMI is disconnected and in the sending process, the
uninstallation driver will be stuck for a long time.
The main problem is that uninstalling the driver waits for curr_msg to
be sent or HOSED. After stopping tasklet, the only place to trigger the
timeout mechanism is the circular poll in shutdown_smi.
The poll function delays 10us and calls smi_event_handler(smi_info,10).
Smi_event_handler deducts 10us from kcs->ibf_timeout.
But the poll func is followed by schedule_timeout_uninterruptible(1).
The time consumed here is not counted in kcs->ibf_timeout.
So when 10us is deducted from kcs->ibf_timeout, at least 1 jiffies has
actually passed. The waiting time has increased by more than a
hundredfold.
Now instead of calling poll(). call smi_event_handler() directly and
calculate the elapsed time.
For verification, you can directly use ebpf to check the kcs->
ibf_timeout for each call to kcs_event() when IPMI is disconnected.
Decrement at normal rate before unloading. The decrement rate becomes
very slow after unloading.
$ bpftrace -e 'kprobe:kcs_event {printf("kcs->ibftimeout : %d\n",
*(arg0+584));}'
Signed-off-by: Zhang Yuchen <zhangyuchen....@bytedance.com>
---
drivers/char/ipmi/ipmi_si_intf.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 6e357ad76f2e..abddd7e43a9a 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -2153,6 +2153,20 @@ static int __init init_ipmi_si(void)
}
module_init(init_ipmi_si);
+static void wait_msg_processed(struct smi_info *smi_info)
+{
+ unsigned long jiffies_now;
+ long time_diff;
+
+ while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
+ jiffies_now = jiffies;
+ time_diff = (((long)jiffies_now -
(long)smi_info->last_timeout_jiffies)
+ * SI_USEC_PER_JIFFY);
+ smi_event_handler(smi_info, time_diff);
+ schedule_timeout_uninterruptible(1);
+ }
+}
+
static void shutdown_smi(void *send_info)
{
struct smi_info *smi_info = send_info;
@@ -2187,16 +2201,13 @@ static void shutdown_smi(void *send_info)
* in the BMC. Note that timers and CPU interrupts are off,
* so no need for locks.
*/
- while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
- poll(smi_info);
- schedule_timeout_uninterruptible(1);
- }
+ wait_msg_processed(smi_info);
+
if (smi_info->handlers)
disable_si_irq(smi_info);
- while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
- poll(smi_info);
- schedule_timeout_uninterruptible(1);
- }
+
+ wait_msg_processed(smi_info);
+
if (smi_info->handlers)
smi_info->handlers->cleanup(smi_info->si_sm);
--
2.30.2
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