openpower-hw-diags/attn/Attention_Handler.md

1 # Attention Handler
6 service from an Attention Handler via an attention signal (e.g. a GPIO). An
7 attention handler is, in this case, a stateless service that handles attention
8 requests. The attention handler in combination with a hardware analyzer
12 attention handler or attention handler service. When operating in application
15 of the attention handler service, per attention signal.
19 The main role of the attention handler is a long running process monitoring the
21 handling attention requests. The attention handler is loaded into memory when
23 When an attention (signal) is detected by the attention handler (monitor) the
24 attention handler will query the state of the host to determine the nature of
27 The attention handler services four types of attentions namely, and in order of
47 The attention handler relies on several external components and BMC services for
53 - systemd: loading and unloading of the attention handler service.
64 - Attention handler starting and stopping: systemd.
68 The attention handler service is started via the BMC systemd infrastructure when
69 the host is started. When the attention handler is started it will register
70 itself as the GPIO event handler associated with the attention GPIO and remain
71 resident in memory waiting for attentions. The attention handler will be stopped
74 If the attention handler terminates due to an error condition it will
75 automatically be restarted by systemd. The attention handler restart policy is
81 When the attention signal becomes active the attention handler will begin
82 handling attentions. Using the PDBG interface the attention handler will query
83 the host to determine the reason for the active attention handler signal. Each
94 dump. The attention handler will wait, up to one hour, for the dump to complete
103 determine the specific type of special attention the attention handler relies on
105 The attention handler gains access to this memory region by submitting a request
112 or a shutdown has been requested. When servicing a HBTI the attention handler
115 For a TI with SRC, using the TI info, the attention handler will create and
118 Optionally, based upon flags in the TI info, the attention handler may mark the
121 For a TI with EID, the attention handler will, based upon flags in the TI info,
123 of the dump the attention handler will request a re-IPL of the host via the dbus
124 interface. For a TI with EID the attention handler will forgo creating a PEL
130 When servicing a PHYPTI the attention handler will generate a PEL entry and then
135 These attentions are used to signal to the attention handler that it should
139 attention is assumed. When a BP attention occurs the attention handler will use
141 encountered. The attention handler will then go back to listening for
148 a TI the attention handler will note whether or not the host is reporting
149 recoverable errors. If recoverable errors are present the attention handler will
157 checkstop attention the attention handler will call the analyzer and then wait
158 for analyses to complete. Once analyses have completed the attention handler
164 Some attention handler behavior can be configured by passing parameters to the
176 Regardless of the type of special attention the attention handler will always
177 create at least one PEL entry containing attention handler specific FFDC. In
181 handler will return to listening for attentions. In most cases no more
187 If the attention handler encounters any errors while servicing an interrupt it