diff --git a/JOURNAL.md b/JOURNAL.md
index 2ca183d..e7e8668 100644
--- a/JOURNAL.md
+++ b/JOURNAL.md
@@ -4342,3 +4342,801 @@ It works, but very slowly:
 
 Let's add the ability to claim a context in the plictool, as I suspect the claim
 may be broken.
+
+## 2024-10-02
+
+Interesting output with ftrace:
+
+
+    <<< NixOS Stage 1 >>>
+
+
+    An error occurred in stage 1 of the boot process, which must mount the
+    root filesystem on `/mnt-root' and then start stage 2.  Press one
+    of the following keys:
+
+      i) to launch an interactive shell
+      f) to start an interactive shell having pid 1 (needed if you want to
+         start stage 2's init manually)
+      r) to reboot immediately
+      *) to ignore the error and continue
+    iStarting interactive shell...
+    ~ # mount -t tracefs nodev /sys/kernel/tracing/
+    ~ # cd /sys/kernel/tracing/
+    /sys/kernel/tracing # cat current_tracer
+    function
+    /sys/kernel/tracing # cat enabled_functions
+    plic_irq_unmask (1)
+    plic_irq_mask (1)
+    plic_dying_cpu (1)
+    plic_starting_cpu (1)
+    plic_irq_domain_translate (1)
+    plic_irq_domain_alloc (1)
+    plic_parse_context_parent (1)
+    plic_irq_set_type (1)
+    plic_toggle.constprop.0 (1)
+    plic_irq_eoi (1)
+    plic_probe (1)
+    plic_irq_suspend (1)
+    plic_handle_irq (1)
+    plic_irq_enable (1)
+    plic_irq_disable (1)
+    plic_irq_resume (1)
+    /sys/kernel/tracing # cat tracing_on
+    1
+    /sys/kernel/tracing # cat trac
+    trace                trace_options        tracing_max_latency
+    trace_clock          trace_pipe           tracing_on
+    trace_marker         trace_stat/          tracing_thresh
+    trace_marker_raw     tracing_cpumask
+    /sys/kernel/tracing # cat trace
+    # tracer: function
+    #
+    # entries-in-buffer/entries-written: 1586/1586   #P:1
+    ...
+    /sys/kernel/tracing # cat options/function-trace
+    1
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	-	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # cat tracing_on
+    1
+    /sys/kernel/tracing # echo 0>tracing_on
+
+    /sys/kernel/tracing # cat tracing_on
+    1
+    /sys/kernel/tracing # echo 0 > tracing_on
+    /sys/kernel/tracing # cat tracing_on
+    0
+    /sys/kernel/tracing # echo plic_handle_irq > set_ftrace_filter
+    /sys/kernel/tracing # cat enabled_functions
+    plic_handle_irq (1)
+    /sys/kernel/tracing # echo plic_handle_irq,plic_irq_eoi,plic_irq_enable,plic_irq
+    _disable > set_ftrace_filter ^C
+
+    /sys/kernel/tracing # echo plic_irq_eoi >> set_ftrace_filter
+    /sys/kernel/tracing # cat enabled_functions
+    plic_irq_eoi (1)
+    plic_handle_irq (1)
+    /sys/kernel/tracing # echo plic_irq_enable >> set_ftrace_filter
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	-	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # ^Ct enabled_functions
+
+    /sys/kernel/tracing # echo hi > /dev/ttyS1
+    ^Z^C
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # echo plic_irq_enable >> set_f^Cace_filter
+
+    /sys/kernel/tracing # cat tracing_on
+    0
+    /sys/kernel/tracing # echo 1 > tracing_on
+    /sys/kernel/tracing # cat tracing_on
+    1
+    /sys/kernel/tracing # cat trace_pipe &
+    /sys/kernel/tracing # fg
+    cat trace_pipe
+    ^Z[1]+  Stopped                    cat trace_pipe
+    /sys/kernel/tracing # bg
+    [1] cat trace_pipe
+    /sys/kernel/tracing # echo hi > /dev/ttyS1
+                 ash-91      [000] d..2.   669.966205: plic_irq_enable <-irq_enable
+                 ash-91      [000] d..2.   669.966815: plic_irq_enable <-irq_enable
+
+    *** local echo: yes ***
+
+    *** local echo: no ***
+    ^C
+    /sys/kernel/tracing # echo 0 > tracing_on
+    /sys/kernel/tracing # cat tracing_on
+    0
+    /sys/kernel/tracing # echo 'plic_*' >> set_ftrace_filter
+    /sys/kernel/tracing # cat enabled_functions
+    plic_irq_unmask (1)
+    plic_irq_mask (1)
+    plic_dying_cpu (1)
+    plic_starting_cpu (1)
+    plic_irq_domain_translate (1)
+    plic_irq_domain_alloc (1)
+    plic_parse_context_parent (1)
+    plic_irq_set_type (1)
+    plic_toggle.constprop.0 (1)
+    plic_irq_eoi (1)
+    plic_probe (1)
+    plic_irq_suspend (1)
+    plic_handle_irq (1)
+    plic_irq_enable (1)
+    plic_irq_disable (1)
+    plic_irq_resume (1)
+    /sys/kernel/tracing # echo 1 > tracing_on
+    /sys/kernel/tracing # cat trace_pipe &
+    /sys/kernel/tracing # cat: can't open 'trace_pipe': Device or resource busy
+
+    [2]+  Done(1)                    cat trace_pipe
+    /sys/kernel/tracing # ps
+    PID   USER     TIME  COMMAND
+        1 0         0:33 {init} /nix/store/y477q6jlbg9b53knnclgib65fbzpazkj-extra-u
+        2 0         0:00 [kthreadd]
+        3 0         0:00 [pool_workqueue_]
+        4 0         0:00 [kworker/R-slub_]
+        5 0         0:00 [kworker/R-netns]
+        6 0         0:00 [kworker/0:0-eve]
+        7 0         0:00 [kworker/0:0H]
+        8 0         0:03 [kworker/u4:0-ev]
+        9 0         0:00 [kworker/R-mm_pe]
+       10 0         0:41 [kworker/u4:1-ev]
+       11 0         0:00 [rcu_tasks_rude_]
+       12 0         0:00 [rcu_tasks_trace]
+       13 0         0:00 [ksoftirqd/0]
+       14 0         0:00 [kworker/0:1-eve]
+       15 0         0:01 [kdevtmpfs]
+       16 0         0:00 [kworker/R-inet_]
+       17 0         0:00 [kauditd]
+       18 0         0:00 [khungtaskd]
+       20 0         0:00 [oom_reaper]
+       21 0         0:00 [kworker/R-write]
+       22 0         0:01 [kcompactd0]
+       23 0         0:00 [ksmd]
+       24 0         0:00 [kworker/R-kinte]
+       25 0         0:00 [kworker/R-kbloc]
+       26 0         0:00 [kworker/R-blkcg]
+       27 0         0:00 [kworker/R-ata_s]
+       28 0         0:00 [kworker/R-devfr]
+       29 0         0:00 [watchdogd]
+       30 0         0:01 [kworker/u4:3-ev]
+       31 0         0:00 [kworker/R-rpcio]
+       32 0         0:00 [kworker/R-xprti]
+       33 0         0:00 [kswapd0]
+       34 0         0:00 [kworker/R-nfsio]
+       35 0         0:00 [kworker/R-kthro]
+       36 0         0:09 [khvcd]
+       37 0         0:00 [kworker/R-uas]
+       38 0         0:00 [kworker/R-mld]
+       39 0         0:00 [kworker/R-ipv6_]
+       46 0         0:00 [kworker/R-kstrp]
+       47 0         0:00 [kworker/u5:0]
+       73 0         0:00 tee -i /proc/self/fd/8
+       74 0         0:00 {init} /nix/store/y477q6jlbg9b53knnclgib65fbzpazkj-extra-u
+       91 0         0:46 /nix/store/y477q6jlbg9b53knnclgib65fbzpazkj-extra-utils/bi
+      113 0         0:00 cat trace_pipe
+      117 0         0:00 ps
+    /sys/kernel/tracing # fg
+    cat trace_pipe
+    ^C
+    /sys/kernel/tracing # cat trace_pipe &
+    /sys/kernel/tracing # echo 1 > tracing_on
+    /sys/kernel/tracing # echo hi > /dev/ttyS1
+                 ash-91      [000] d..2.   748.552248: plic_irq_enable <-irq_enable
+                 ash-91      [000] d..2.   748.552370: plic_toggle.constprop.0 <-plic_irq_enable
+                 ash-91      [000] d..2.   748.552797: plic_irq_disable <-irq_disable
+                 ash-91      [000] d..2.   748.552858: plic_toggle.constprop.0 <-plic_irq_disable
+                 ash-91      [000] d..2.   748.553102: plic_irq_enable <-irq_enable
+                 ash-91      [000] d..2.   748.553163: plic_toggle.constprop.0 <-plic_irq_enable
+    ^C
+    /sys/kernel/tracing #              ash-91      [000] d..2.   762.013481: plic_irq_disable <-__irq_disable
+                 ash-91      [000] d..2.   762.013603: plic_toggle.constprop.0 <-plic_irq_disable
+
+    /sys/kernel/tracing #
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # plictool -C 1
+    0
+    /sys/kernel/tracing # plictool -C 1 -w 4
+    /sys/kernel/tracing # plictool -C 1
+    0
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # devmem 0x40014000 32 0xffffffff
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # plictool -C 1 -w 4
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # plictool -E
+    plictool: option requires an argument: E
+    plictool v0.0.5 -- Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
+    Usage:
+      plictool [-a addr] [-L] [-n nsrc] [-x nctx]  # List (default)
+      plictool [-a addr] -C ctx [-w value]         # Claim
+      plictool [-a addr] -T ctx [-w value]         # Threshold
+      plictool [-a addr] -I src [-w value]         # Priority
+      plictool [-a addr] -P src [-w value]         # Pending
+      plictool [-a addr] -E src -c ctx [-w value]  # Enabled
+      plictool -v                                  # Version
+    /sys/kernel/tracing # plictool -E 4 -c 0 -w 1
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	masked	-
+    36	-	0	masked	-
+    /sys/kernel/tracing # plictool -C 0
+    4
+    /sys/kernel/tracing # plictool -C 0 -w 4
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	-	1	masked	-
+    36	-	0	masked	-
+    /sys/kernel/tracing # plictool -E 4 -c 0 -w 0
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	-	1	-	-
+    /sys/kernel/tracing # cat /dev/ttyS1 &
+    /sys/kernel/tracing #              cat-136     [000] d..2.   887.106509: plic_irq_enable <-irq_enable
+                 cat-136     [000] d..2.   887.106631: plic_toggle.constprop.0 <-plic_irq_enable
+                 cat-136     [000] d.h2.   887.106814: plic_handle_irq <-generic_handle_domain_irq
+                 cat-136     [000] d.h3.   887.106997: plic_irq_eoi <-handle_fasteoi_irq
+                 cat-136     [000] d..2.   887.107424: plic_irq_disable <-irq_disable
+                 cat-136     [000] d..2.   887.107546: plic_toggle.constprop.0 <-plic_irq_disable
+                 cat-136     [000] d..2.   887.107729: plic_irq_enable <-irq_enable
+                 cat-136     [000] d..2.   887.107790: plic_toggle.constprop.0 <-plic_irq_enable
+
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	firing
+    2	-	1	-	-
+    3	-	1	-	-
+    4	-	1	-	-
+    33	-	0	-	masked
+
+So, then an interrupt is fired, we disable the interrupts and then we enable
+them again. Can this happen because the next interrupt fired when interrupts
+were disabled?
+
+There are also other cases in which we already have an interrupt pending and we
+enable the context 1. For example, by setting the enable bit, changing the prio,
+or the threshold for that context or by removing the context 0 enable bit.
+
+I think I can do some tests with those. I'm not sure why the serial port is
+firing an interrupt, but if this is the case, I can try to write a character in
+the transmit register and wait for the pending bit, then try to claim the
+interrupt for source 1.
+
+## 2024-10-03
+
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    /sys/kernel/tracing # cat tracing_on
+    1
+    /sys/kernel/tracing # echo 0 > tracing_on
+    /sys/kernel/tracing # echo 1 > tracing_on
+    /sys/kernel/tracing # cat trace_pipe &
+    /sys/kernel/tracing # cat /dev/ttyS1 &
+    /sys/kernel/tracing #              cat-122     [000] ...1.  2978.202587: serial8250_pm <-uart_port_startup
+                 cat-122     [000] ...1.  2978.202648: serial8250_set_sleep <-serial8250_pm
+                 cat-122     [000] ...1.  2978.202892: serial8250_startup <-uart_port_startup
+                 cat-122     [000] ...1.  2978.203014: serial8250_do_startup <-serial8250_startup
+                 cat-122     [000] d..2.  2978.203319: plic_irq_enable <-irq_enable
+                 cat-122     [000] d..2.  2978.203380: plic_toggle.constprop.0 <-plic_irq_enable
+                 cat-122     [000] d.h2.  2978.203563: plic_handle_irq <-generic_handle_domain_irq
+                 cat-122     [000] d.h2.  2978.203685: serial8250_interrupt <-__handle_irq_event_percpu
+                 cat-122     [000] d.h3.  2978.203746: serial8250_default_handle_irq <-serial8250_interrupt
+                 cat-122     [000] d.h3.  2978.203807: serial8250_handle_irq <-serial8250_default_handle_irq
+                 cat-122     [000] d.h3.  2978.203990: plic_irq_eoi <-handle_fasteoi_irq
+                 cat-122     [000] d..2.  2978.204783: plic_irq_disable <-irq_disable
+                 cat-122     [000] d..2.  2978.204844: plic_toggle.constprop.0 <-plic_irq_disable
+                 cat-122     [000] d..2.  2978.205088: plic_irq_enable <-irq_enable
+                 cat-122     [000] d..2.  2978.205149: plic_toggle.constprop.0 <-plic_irq_enable
+                 cat-122     [000] d..2.  2978.205271: serial8250_do_set_mctrl <-serial8250_do_startup
+                 cat-122     [000] ...1.  2978.205393: serial8250_set_termios <-uart_change_line_settings
+                 cat-122     [000] ...1.  2978.206796: serial8250_do_set_termios <-serial8250_set_termios
+                 cat-122     [000] .n.1.  2978.206918: serial8250_get_divisor <-serial8250_do_set_termios
+                 cat-122     [000] dn.2.  2978.207040: serial8250_do_set_divisor <-serial8250_do_set_termios
+                 cat-122     [000] dn.2.  2978.207101: serial8250_do_set_mctrl <-serial8250_do_set_termios
+                 cat-122     [000] dn.2.  2978.207345: serial8250_set_mctrl <-uart_update_mctrl
+                 cat-122     [000] dn.2.  2978.207406: serial8250_do_set_mctrl <-serial8250_set_mctrl
+
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	firing
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    33	-	0	-	masked
+    /sys/kernel/tracing # plictool -C 1
+    0
+
+Another test tracing the UART serial too.
+
+It would be nice to see where those calls are coming from.
+
+Let's collect the commands I need to use here:
+
+    mount -t tracefs nodev /sys/kernel/tracing/
+    cd /sys/kernel/tracing/
+    echo 'plic_*' >> set_ftrace_filter
+    echo 'serial8250_*' >> set_ftrace_filter
+    cat current_tracer
+
+Here is a trace with the stack trace printed:
+
+    ~ # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	-	1	-	-
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+
+    ~ #
+    [...]
+    /sys/kernel/tracing # cat /dev/ttyS1 &
+
+                 cat-122     [000] .....   591.693894: serial8250_pm <-uart_port_startup
+                 cat-122     [000] .....   591.694077: <stack trace>
+     => ftrace_call
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .....   591.694138: serial8250_set_sleep <-serial8250_pm
+                 cat-122     [000] .....   591.694260: <stack trace>
+     => ftrace_call
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .....   591.694504: serial8250_startup <-uart_port_startup
+                 cat-122     [000] .....   591.694687: <stack trace>
+     => ftrace_call
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .....   591.694748: serial8250_do_startup <-serial8250_startup
+                 cat-122     [000] .....   591.694870: <stack trace>
+     => ftrace_call
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.695236: plic_irq_enable <-irq_enable
+                 cat-122     [000] d..1.   591.695358: <stack trace>
+     => ftrace_call
+     => irq_startup
+     => __setup_irq
+     => request_threaded_irq
+     => univ8250_setup_irq
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.695480: plic_toggle.constprop.0 <-plic_irq_enable
+                 cat-122     [000] d..1.   591.695602: <stack trace>
+     => ftrace_call
+     => irq_enable
+     => irq_startup
+     => __setup_irq
+     => request_threaded_irq
+     => univ8250_setup_irq
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.696456: plic_irq_disable <-irq_disable
+                 cat-122     [000] d..1.   591.696578: <stack trace>
+     => ftrace_call
+     => __disable_irq_nosync
+     => disable_irq_nosync
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.696639: plic_toggle.constprop.0 <-plic_irq_disable
+                 cat-122     [000] d..1.   591.696822: <stack trace>
+     => ftrace_call
+     => irq_disable
+     => __disable_irq_nosync
+     => disable_irq_nosync
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.697005: plic_irq_enable <-irq_enable
+                 cat-122     [000] d..1.   591.697188: <stack trace>
+     => ftrace_call
+     => irq_startup
+     => __enable_irq
+     => enable_irq
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d..1.   591.697249: plic_toggle.constprop.0 <-plic_irq_enable
+                 cat-122     [000] d..1.   591.697432: <stack trace>
+     => ftrace_call
+     => irq_enable
+     => irq_startup
+     => __enable_irq
+     => enable_irq
+     => serial8250_do_startup
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] d.h1.   591.697554: plic_handle_irq <-generic_handle_domain_irq
+                 cat-122     [000] d.h1.   591.697676: <stack trace>
+     => ftrace_call
+     => riscv_intc_irq
+     => handle_riscv_irq
+     => call_on_irq_stack
+     => 0x1c003b9260
+                 cat-122     [000] d.h1.   591.697798: serial8250_interrupt <-__handle_irq_event_percpu
+                 cat-122     [000] d.h1.   591.697920: <stack trace>
+     => ftrace_call
+     => handle_irq_event
+     => handle_fasteoi_irq
+     => generic_handle_domain_irq
+     => plic_handle_irq
+     => generic_handle_domain_irq
+     => riscv_intc_irq
+     => handle_riscv_irq
+     => call_on_irq_stack
+     => 0x1c001dc940
+                 cat-122     [000] d.h2.   591.697981: serial8250_default_handle_irq <-serial8250_interrupt
+                 cat-122     [000] d.h2.   591.698103: <stack trace>
+     => ftrace_call
+     => __handle_irq_event_percpu
+     => handle_irq_event
+     => handle_fasteoi_irq
+     => generic_handle_domain_irq
+     => plic_handle_irq
+     => generic_handle_domain_irq
+     => riscv_intc_irq
+     => handle_riscv_irq
+     => call_on_irq_stack
+     => 0x1c001dc940
+                 cat-122     [000] d.h2.   591.698164: serial8250_handle_irq <-serial8250_default_handle_irq
+                 cat-122     [000] d.h2.   591.698286: <stack trace>
+     => ftrace_call
+     => serial8250_interrupt
+     => __handle_irq_event_percpu
+     => handle_irq_event
+     => handle_fasteoi_irq
+     => generic_handle_domain_irq
+     => plic_handle_irq
+     => generic_handle_domain_irq
+     => riscv_intc_irq
+     => handle_riscv_irq
+     => call_on_irq_stack
+     => 0x1c00595ba0
+                 cat-122     [000] d.h2.   591.698469: plic_irq_eoi <-handle_fasteoi_irq
+                 cat-122     [000] d.h2.   591.698530: <stack trace>
+     => ftrace_call
+     => generic_handle_domain_irq
+     => plic_handle_irq
+     => generic_handle_domain_irq
+     => riscv_intc_irq
+     => handle_riscv_irq
+     => call_on_irq_stack
+     => 0x1c00595ba0
+                 cat-122     [000] d..1.   591.698713: serial8250_do_set_mctrl <-serial8250_do_startup
+                 cat-122     [000] d..1.   591.698835: <stack trace>
+     => ftrace_call
+     => serial8250_startup
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .n...   591.700177: serial8250_set_termios <-uart_change_line_settings
+                 cat-122     [000] .n...   591.700299: <stack trace>
+     => ftrace_call
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .n...   591.700421: serial8250_do_set_termios <-serial8250_set_termios
+                 cat-122     [000] .n...   591.700543: <stack trace>
+     => ftrace_call
+     => uart_change_line_settings
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] .n...   591.700604: serial8250_get_divisor <-serial8250_do_set_termios
+                 cat-122     [000] .n...   591.700787: <stack trace>
+     => ftrace_call
+     => serial8250_set_termios
+     => uart_change_line_settings
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] dn.1.   591.700909: serial8250_do_set_divisor <-serial8250_do_set_termios
+                 cat-122     [000] dn.1.   591.701031: <stack trace>
+     => ftrace_call
+     => serial8250_set_termios
+     => uart_change_line_settings
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] dn.1.   591.701092: serial8250_do_set_mctrl <-serial8250_do_set_termios
+                 cat-122     [000] dn.1.   591.701214: <stack trace>
+     => ftrace_call
+     => serial8250_set_termios
+     => uart_change_line_settings
+     => uart_port_startup
+     => uart_port_activate
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] dn.1.   591.701458: serial8250_set_mctrl <-uart_update_mctrl
+                 cat-122     [000] dn.1.   591.701580: <stack trace>
+     => ftrace_call
+     => uart_dtr_rts
+     => tty_port_block_til_ready
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+                 cat-122     [000] dn.1.   591.701702: serial8250_do_set_mctrl <-serial8250_set_mctrl
+                 cat-122     [000] dn.1.   591.701885: <stack trace>
+     => ftrace_call
+     => uart_update_mctrl
+     => uart_dtr_rts
+     => tty_port_block_til_ready
+     => tty_port_open
+     => uart_open
+     => tty_open
+     => chrdev_open
+     => do_dentry_open
+     => vfs_open
+     => path_openat
+     => do_filp_open
+     => do_sys_openat2
+     => __riscv_sys_openat
+     => do_trap_ecall_u
+     => ret_from_exception
+
+    /sys/kernel/tracing # plictool
+    Source	Pend	Prio	C0(7)	C1(0)
+    1	yes	1	-	firing
+    2	-	1	-	-
+    3	-	1	-	-
+    4	yes	1	-	-
+    33	-	0	-	masked
+
+    /sys/kernel/tracing # plictool -C 1
+    0
+
+## 2024-10-04
+
+To trace which accesses are done to the PLIC, I can use the mmiotracer, which
+will hopefully record how we configure the PLIC and lead to a reproducer.
+
+    CONFIG_MMIOTRACE=y