git: b9827c007a7a - main - Revert "dtrace: make 'ring' and 'fill' policies imply 'noswitch' flag"

The branch main has been updated by avg:

URL: https://cgit.FreeBSD.org/src/commit/?id=b9827c007a7a39c7aeef73f8efc217b7b0099464

commit b9827c007a7a39c7aeef73f8efc217b7b0099464
Author:     Andriy Gapon <avg@FreeBSD.org>
AuthorDate: 2024-04-21 10:07:36 +0000
Commit:     Andriy Gapon <avg@FreeBSD.org>
CommitDate: 2024-04-21 12:17:08 +0000

    Revert "dtrace: make 'ring' and 'fill' policies imply 'noswitch' flag"
    
    This reverts commit e92491d95ff3500e140eafa614e88ca84ffb0d26.
    
    The general idea looked good to me.  In particular, it allowed to save
    some memory and avoid memory allocation failures when a large buffer
    size was requested along with ring and fill policies.
    
    But I didn't take into account that the second, supposedly unused
    buffer, was actually used as the scratch buffer.  The scratch buffer is
    used as a temporary space for DTrace subroutines like copyin, copyinstr,
    and alloca.
    
    I think that the change can be fixed by allocating a separate smaller
    buffer for the scratch buffer, but that fix would require more work than
    I am able to do now.  Hence the revert.
    
    Reported by:    Domagoj Stolfa
    Diagnosed by:   Domagoj Stolfa, markj
    MFC after:      immediately
---
 sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
index 83c0648b23b1..ce02676e0dc1 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
@@ -12058,6 +12058,7 @@ dtrace_buffer_switch(dtrace_buffer_t *buf)
 	hrtime_t now;
 
 	ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
+	ASSERT(!(buf->dtb_flags & DTRACEBUF_RING));
 
 	cookie = dtrace_interrupt_disable();
 	now = dtrace_gethrtime();
@@ -14865,10 +14866,10 @@ dtrace_state_buffer(dtrace_state_t *state, dtrace_buffer_t *buf, int which)
 
 	if (which == DTRACEOPT_BUFSIZE) {
 		if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_RING)
-			flags |= DTRACEBUF_RING | DTRACEBUF_NOSWITCH;
+			flags |= DTRACEBUF_RING;
 
 		if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_FILL)
-			flags |= DTRACEBUF_FILL | DTRACEBUF_NOSWITCH;
+			flags |= DTRACEBUF_FILL;
 
 		if (state != dtrace_anon.dta_state ||
 		    state->dts_activity != DTRACE_ACTIVITY_ACTIVE)