rcu/torture: Improve badness extraction from console logs

Currently console.log.diags contains an output like follows:
[ 2457.293734] WARNING: CPU: 2 PID: 13 at kernel/rcu/tasks.h:1061 rcu_tasks_trace_pregp_step+0x4a/0x50
[ 2457.542385] Call Trace:

This is not very useful and the Call trace is desired. Improve the
script by Extracting more lines after each grep match.

With this the above becomes:

Issue 1:
[ 2457.293734] WARNING: CPU: 2 PID: 13 at kernel/rcu/tasks.h:1061 rcu_tasks_trace_pregp_step+0x4a/0x50
[ 2457.326661] Modules linked in:
[ 2457.334818] CPU: 2 PID: 13 Comm: rcu_tasks_trace Not tainted 5.15.128+ torvalds#381
[ 2457.349782] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[ 2457.373309] RIP: 0010:rcu_tasks_trace_pregp_step+0x4a/0x50
[ 2457.386691] Code: 48 63 c7 48 8b 0
[ 2457.421803] RSP: 0018:ffffa80fc0073e40 EFLAGS: 00010202
[ 2457.431940] RAX: ffff8db91f580000 RBX: 000000000001b900 RCX: 0000000000000003
[ 2457.443206] RDX: 0000000000000008 RSI: ffffffffac6bebd8 RDI: 0000000000000003
[ 2457.454428] RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000001
[ 2457.465668] R10: 0000000000000000 R11: 00000000ffffffff R12: ffff8db902d87f40
[ 2457.476971] R13: ffffffffac556620 R14: ffffffffac556630 R15: ffff8db9011a3200
[ 2457.488251] FS:  0000000000000000(0000) GS:ffff8db91f500000(0000) knlGS:0000000000000000
[ 2457.500834] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2457.509602] CR2: 0000000000000000 CR3: 0000000002cbc000 CR4: 00000000000006e0
[ 2457.520378] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2457.531440] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2457.542385] Call Trace:
[ 2457.546756]  <TASK>
[ 2457.550349]  ? __warn+0x7b/0x100
[ 2457.567214]  ? rcu_tasks_trace_pregp_step+0x4a/0x50
-------------------------------------
Issue 2:
[ 2457.542385] Call Trace:
[ 2457.546756]  <TASK>
[ 2457.550349]  ? __warn+0x7b/0x100
[ 2457.567214]  ? rcu_tasks_trace_pregp_step+0x4a/0x50
[ 2457.574948]  ? report_bug+0x99/0xc0
[ 2457.593824]  ? handle_bug+0x3c/0x70
[ 2457.599534]  ? exc_invalid_op+0x13/0x60
[ 2457.625729]  ? asm_exc_invalid_op+0x16/0x20
[ 2457.632249]  ? rcu_tasks_trace_pregp_step+0x4a/0x50
[ 2457.660010]  rcu_tasks_wait_gp+0x54/0x360
[ 2457.677761]  ? _raw_spin_unlock_irqrestore+0x2b/0x60
[ 2457.705658]  rcu_tasks_kthread+0x114/0x200
[ 2457.712450]  ? wait_woken+0x70/0x70
[ 2457.727283]  ? synchronize_rcu_tasks_rude+0x10/0x10
[ 2457.746221]  kthread+0x130/0x160
[ 2457.751487]  ? set_kthread_struct+0x40/0x40
[ 2457.758178]  ret_from_fork+0x22/0x30
[ 2457.763909]  </TASK>
[ 2457.767546] irq event stamp: 29544441
[ 2457.773344] hardirqs last  enabled at (29544451): [<ffffffffaace6cbd>] __up_console_sem+0x4d/0x60
[ 2457.786967] hardirqs last disabled at (29544460): [<ffffffffaace6ca2>] __up_console_sem+0x32/0x60
-------------------------------------

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Author: joelagnel

tools/testing/selftests/rcutorture/bin/console-badness.sh

@@ -9,10 +9,32 @@
 # Copyright (C) 2020 Facebook, Inc.
 #
 # Authors: Paul E. McKenney <paulmck@kernel.org>
+INPUT_DATA=$(< /dev/stdin)
 
-grep -E 'Badness|WARNING:|Warn|BUG|===========|BUG: KCSAN:|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for|!!!' |
+# Get the line numbers for all the grep matches
+GREP_LINES="$(echo "$INPUT_DATA" |
+grep -n -E 'Badness|WARNING:|Warn|BUG|===========|BUG: KCSAN:|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for|!!!' |
 grep -v 'ODEBUG: ' |
 grep -v 'This means that this is a DEBUG kernel and it is' |
 grep -v 'Warning: unable to open an initial console' |
 grep -v 'Warning: Failed to add ttynull console. No stdin, stdout, and stderr.*the init process!' |
 grep -v 'NOHZ tick-stop error: Non-RCU local softirq work is pending, handler'
+)"
+
+# Exit if no grep matches
+if [ ! -n "$GREP_LINES" ]; then exit 0; fi
+
+# Go through each line of GREP_LINES, extract the line number and then
+# print from that line and 20 lines after that line. Do that for each
+# grep match.
+issue_num=1
+while IFS= read -r line; do
+    # Extract the line number from the line
+    num=$(echo "$line" | awk -F: '{print $1}')
+    # Print 20 lines after the matched line
+    echo "Issue $issue_num:"
+    issue_num="$(($issue_num + 1))"
+    echo "$INPUT_DATA" | sed -n "${num},$(($num + 20))p"
+    echo "-------------------------------------"
+done <<< "$GREP_LINES"
+