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scylla-gdb.py: scylla fiber: add suggestion for further investigation

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scylla fiber often fails to really unwind the entire fiber, stopping
sooner than expected. This is expected as scylla fiber only recognizes
the most standard continuations but can drop the ball as soon as there
is an unusual transmission.
This commits adds a message below the found tasks explaining that the
list might not be exhaustive and prints a command which can be used to
explain why the unwinding stopped at the last task.

While at it also rephrase an out-of-date comment.

Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20200710120813.100009-1-bdenes@scylladb.com>
This commit is contained in:
Botond Dénes
2020-07-10 15:08:13 +03:00
committed by Avi Kivity
parent 29fccd76ea
commit ef2c8f563b
1 changed files with 10 additions and 3 deletions
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13
scylla-gdb.py
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@@ -2571,8 +2571,8 @@ class scylla_fiber(gdb.Command):
The pattern we are looking for is:
ptr -> vtable ptr for a symbol that matches our whitelist
In addition, ptr has to point to a the beginning of an allocation
block, managed by seastar, that contains a live object.
In addition, ptr has to point to an allocation block, managed by
seastar, that contains a live object.
"""
try:
maybe_vptr = int(gdb.Value(ptr).reinterpret_cast(self._vptr_type).dereference())
@@ -2677,13 +2677,20 @@ class scylla_fiber(gdb.Command):
return
try:
this_task, fiber = self._walk(int(gdb.parse_and_eval(args.task)), args.max_depth, args.scanned_region_size, args.force_fallback_mode, args.verbose)
initial_task_ptr = int(gdb.parse_and_eval(args.task))
this_task, fiber = self._walk(initial_task_ptr, args.max_depth, args.scanned_region_size, args.force_fallback_mode, args.verbose)
tptr, vptr, name = this_task
gdb.write("Starting task: (task*) 0x{:016x} 0x{:016x} {}\n".format(tptr.ptr, int(vptr), name))
for i, (tptr, vptr, name) in enumerate(fiber):
gdb.write("#{:<2d} (task*) 0x{:016x} 0x{:016x} {}\n".format(i, int(tptr), int(vptr), name))
gdb.write("\nFound no further pointers to task objects.\n")
if not fiber:
gdb.write("If this is unexpected, run `scylla fiber 0x{:016x} --verbose` to learn more.\n".format(initial_task_ptr))
else:
gdb.write("If you think there should be more, run `scylla fiber 0x{:016x} --verbose` to learn more.\n".format(fiber[-1][0]))
except KeyboardInterrupt:
return