Re: [RFC PATCH 0/4] utrace: new modular infrastructure for user debug/tracing

[Frank Ch. Eigler]

Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx> writes:

> [...]  Renzo Davoli also posted a patch to allow "batching" of
> ptrace requests and Systemptap really needs this, too.  AFAICT this
> can be done by writing a custom engine. [...]

Indeed, I like what I see (at least those parts I understand) in
roland's utrace code.  One missed opportunity bit appears to be any
new support for something like per-thread breakpoints.

If I correctly understand how gdb etc. work, a hit breakpoint involves
stoppage of all other threads of a process, then the breakpoint
instruction is replaced by the original one, then the thread is
single-stepped, then the breakpoint is put back, then finally all
threads are resumed.  Could utrace API provide short-lived per-thread
page copies to execute the single-stepped original instruction out of,
and avoid stopping & resuming all other threads?

- FChE
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