Date: Tue, 03 Oct 2017 10:51:19 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 222752] DTrace: probe syscall::write:entry is not fired unless printf in action Message-ID: <bug-222752-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222752 Bug ID: 222752 Summary: DTrace: probe syscall::write:entry is not fired unless printf in action Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: hannes@mehnert.org I'm using rev322062, compiled (cc -o t t.c) the t.c below, which is a quite small test case just for this bug. The lifecycle of t and DTrace are not equal - thus I try to communicate from the user application (t) to DTrace when to start instrumenting and when to stop. I do this by t writing START and STOP onto stdout, and the D script to set a thread-local variable. The probe sysctl::write:entry in t.d is not executed - the same one in t2.d, where a printf is added - is executed. My expectation from DTace is that t.d's sysctl::write:entry would also be executed. I execute "doas ./d.t" in one shell, then execute ./t in another shell. (Running dtrace -c obviously works because DTrace then exits once t exits, but this is not a solution for my use case (a much bigger instrumentation where I only want to trace after some initialisation). t.c ============================== #include <stdio.h> #include <unistd.h> int main (int argc, char ** argv) { printf("START"); printf("BOOOOOOOO\n"); printf("STOP"); printf("done now\n"); } ============================== t.d ============================== #!/usr/sbin/dtrace -Cs #pragma D option quiet #define prog "t" #define act execname == prog && self->started == 1 syscall::write:entry /arg0 == 1 && (string)copyin(arg1, 5) == "START"/ { self->started = 1; } syscall::write:entry /act && arg0 == 1 && (string)copyin(arg1, 4) == "STOP" && self->started == 1/ { exit(0); } ============================== t2.d ============================== #!/usr/sbin/dtrace -Cs #pragma D option quiet #define prog "t" #define act execname == prog && self->started == 1 syscall::write:entry /arg0 == 1 && (string)copyin(arg1, 5) == "START"/ { printf("starting\n"); self->started = 1; } syscall::write:entry /act && arg0 == 1 && (string)copyin(arg1, 4) == "STOP" && self->started == 1/ { printf("exiting now\n"); exit(0); } ============================== -- You are receiving this mail because: You are the assignee for the bug.
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