[Bug gdb/30695] New: [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution

[Bug gdb/30695] New: [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30695

            Bug ID: 30695
           Summary: [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp:
                    no force memory write: SIGINT does not interrupt
                    background execution
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

With an -fsanitize=thread build, I ran into:
...
FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does
not interrupt background execution
FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: force memory write: SIGINT does not
interrupt background execution
...

The first in more detail:
...
(gdb) PASS: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: break
foo if <condition>
c&^M
Continuing.^M
(gdb) ^M
Breakpoint 2, foo () at
/labs/tdevries/gdb/src/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.c:23^M
23        return 0;^M
FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does
not interrupt background execution
...

Instead, we expect to see:
...
(gdb) PASS: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: break
foo if <condition>
c&^M
Continuing.^M
(gdb) Quit^M
(gdb) quit_count=1
Quit^M
(gdb) quit_count=2
Quit^M
(gdb) quit_count=3
Quit^M
(gdb) quit_count=4
Quit^M
(gdb) quit_count=5
Quit^M
(gdb) quit_count=6
Quit^M
(gdb) quit_count=7
Quit^M
(gdb) quit_count=8
Quit^M
(gdb) quit_count=9
Quit^M
(gdb) quit_count=10
^M
Breakpoint 2, foo () at
/data/vries/gdb/src/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.c:23^M
23        return 0;^M
PASS: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does
not interrupt background execution
...

Triggering this may be a timing issue, this is on a fast server with lots of
memory.

On my laptop, the test passes with an -fsanitize=thread build.

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[Bug gdb/30695] [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30695

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #0)
> On my laptop, the test passes with an -fsanitize=thread build.

Scrap that, now also reproduces on my laptop.

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[Bug gdb/30695] [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30695

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
From https://www.gnu.org/software/libc/manual/html_node/Merged-Signals.html:
...
If multiple signals of the same type are delivered to your process before your
signal handler has a chance to be invoked at all, the handler may only be
invoked once, as if only a single signal had arrived. In effect, the signals
merge into one. This situation can arise when the signal is blocked, or in a
multiprocessing environment where the system is busy running some other
processes while the signals are delivered. This means, for example, that you
cannot reliably use a signal handler to count signals. The only distinction you
can reliably make is whether at least one signal has arrived since a given time
in the past. 
...

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[Bug gdb/30695] [gdb, tsan] FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30695

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |palves at sourceware dot org

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Pedro, cc-ing you because you wrote the test-case.

To me it looks like the test-case needs fixing because it doesn't take signal
merging into account.  WDYT?

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