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ipmi: fix long wait in unload when IPMI disconnect 

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.lcr@bytedance.com>
Message-Id: <20221007092617.87597-3-zhangyuchen.lcr@bytedance.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Zhang Yuchen 2022-10-07 17:26:16 +08:00 committed by Corey Minyard
parent f90bc0f97f
commit f6f1234d98
1 changed files with 19 additions and 8 deletions
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27
drivers/char/ipmi/ipmi_si_intf.c
View File

@ -2153,6 +2153,20 @@ static int __init init_ipmi_si(void)
} }
module_init(init_ipmi_si); 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) static void shutdown_smi(void *send_info)
{ {
struct smi_info *smi_info = 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, * in the BMC. Note that timers and CPU interrupts are off,
* so no need for locks. * so no need for locks.
*/ */
while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) { wait_msg_processed(smi_info);
poll(smi_info);
schedule_timeout_uninterruptible(1);
}
if (smi_info->handlers) if (smi_info->handlers)
disable_si_irq(smi_info); disable_si_irq(smi_info);
while (smi_info->curr_msg || (smi_info->si_state != SI_NORMAL)) {
poll(smi_info); wait_msg_processed(smi_info);
schedule_timeout_uninterruptible(1);
}
if (smi_info->handlers) if (smi_info->handlers)
smi_info->handlers->cleanup(smi_info->si_sm); smi_info->handlers->cleanup(smi_info->si_sm);