[tip: perf/urgent] perf/hw_breakpoint: Clear stop state in hw_breakpoint_add()

[tip-bot2 for Paolo Bertinetti]

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     6bea5e29daf123a78ae58cb5926023f4705f396f
Gitweb:        https://git.kernel.org/tip/6bea5e29daf123a78ae58cb5926023f4705f396f
Author:        Paolo Bertinetti <paolobertinetti200f4@xxxxxxxxx>
AuthorDate:    Tue, 03 Nov 2026 13:07:53 
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 06 Nov 2026 11:45:14 +01:00

perf/hw_breakpoint: Clear stop state in hw_breakpoint_add()

Since commit 18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage"),
__perf_event_overflow() stops the event with pmu->stop() and disables
it when the PERF_EVENT_IOC_REFRESH limit is reached. When userspace
re-arms the event with PERF_EVENT_IOC_REFRESH, the event is enabled
again and pmu->add() is called with PERF_EF_START.

hw_breakpoint_add() sets PERF_HES_STOPPED when PERF_EF_START is
missing, but never clears it. The flag set by pmu->stop() stays, and
perf_bp_event() drops every later hit, so a breakpoint re-armed this
way delivers only its first overflow.

Set the state from PERF_EF_START on every add, as perf_swevent_add()
does.

Fixes: 18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage")
Assisted-by: LLM
Signed-off-by: Paolo Bertinetti <paolobertinetti200f4@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20261103130732.764081-3-paolobertinetti200f4@xxxxxxxxx
---
 kernel/events/hw_breakpoint.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 789add0..7a60621 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -968,8 +968,7 @@ static int hw_breakpoint_event_init(struct perf_event *bp)
 
 static int hw_breakpoint_add(struct perf_event *bp, int flags)
 {
-	if (!(flags & PERF_EF_START))
-		bp->hw.state = PERF_HES_STOPPED;
+	bp->hw.state = (flags & PERF_EF_START) ? 0 : PERF_HES_STOPPED;
 
 	if (is_sampling_event(bp)) {
 		bp->hw.last_period = bp->hw.sample_period;