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powerpc/perf: fix preempt count underflow in fsl_emb_pmu_del

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fsl_emb_pmu_del() unconditionally calls put_cpu_var(cpu_hw_events) at
the 'out:' label, but only calls the matching get_cpu_var() after the
'i < 0' early-return check. When event->hw.idx is negative the
function jumps to 'out:' without having taken get_cpu_var(), and the
trailing put_cpu_var() then issues an unmatched preempt_enable(),
underflowing preempt_count.

On a CONFIG_PREEMPT=y kernel preempt_count would underflow and
eventually present as a 'scheduling while atomic' BUG.

Move put_cpu_var() to pair with get_cpu_var() so the percpu access is
correctly bracketed and the 'out:' label only handles perf_pmu_enable.

Fixes: a11106544f ("powerpc/perf: e500 support")
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260605082912.305100-2-aboorvad@linux.ibm.com
This commit is contained in:
Aboorva Devarajan 2026-06-05 13:59:10 +05:30 committed by Madhavan Srinivasan
parent 97f902dd4c
commit 81e3a86030
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/perf/core-fsl-emb.c
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@ -366,9 +366,10 @@ static void fsl_emb_pmu_del(struct perf_event *event, int flags)
cpuhw->n_events--;
put_cpu_var(cpu_hw_events);
out:
perf_pmu_enable(event->pmu);
put_cpu_var(cpu_hw_events);
}
static void fsl_emb_pmu_start(struct perf_event *event, int ef_flags)