git: f12a50fed2df - stable/13 - Revert "dtrace: make 'ring' and 'fill' policies imply 'noswitch' flag"

The branch stable/13 has been updated by avg:

URL: https://cgit.FreeBSD.org/src/commit/?id=f12a50fed2df3994b05d7c8702f06bb117c156d6

commit f12a50fed2df3994b05d7c8702f06bb117c156d6
Author:     Andriy Gapon <avg@FreeBSD.org>
AuthorDate: 2024-04-21 10:07:36 +0000
Commit:     Andriy Gapon <avg@FreeBSD.org>
CommitDate: 2024-04-21 12:28:59 +0000

    Revert "dtrace: make 'ring' and 'fill' policies imply 'noswitch' flag"
    
    This reverts commit e92491d95ff3500e140eafa614e88ca84ffb0d26.
    It was cherry-picked as f0ed49921c2891733b7ee65679a8dcba5398e3b6.
    
    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
    
    (cherry picked from commit b9827c007a7a39c7aeef73f8efc217b7b0099464)
---
 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 17d9536b2428..6ae0322ebb0f 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
@@ -12055,6 +12055,7 @@ 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();
@@ -14862,10 +14863,10 @@ 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)