From: Vineet Gupta vgupta@synopsys.com
commit 8c42a5c02bec6c7eccf08957be3c6c8fccf9790b upstream.
commit feb92d7d3813456c11dce21 "(ARC: perf: don't bail setup if pct irq missing in device-tree)" introduced a silly brown-paper bag bug: The assignment and comparison in an if statement were not bracketed correctly leaving the order of evaluation undefined.
| | if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) { | ^^^ ^^^^
And given such a chance, the compiler will bite you hard, fully entitled to generating this piece of beauty:
| | # if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) { | | bl.d @platform_get_irq <-- irq returned in r0 | | setge r2, r0, 0 <-- r2 is bool 1 or 0 if irq >= 0 true/false | brlt.d r0, 0, @.L114 | | st_s r2,[sp] <-- irq saved is bool 1 or 0, not actual return val | st 1,[r3,160] # arc_pmu.18_29->irq <-- drops bool and assumes 1 | | # return __request_percpu_irq(irq, handler, 0, | | bl.d @__request_percpu_irq; | mov_s r0,1 <-- drops even bool and assumes 1 which fails
With the snafu fixed, everything is as expected.
| bl.d @platform_get_irq <-- returns irq in r0 | | mov_s r2,r0 | brlt.d r2, 0, @.L112 | | st_s r0,[sp] <-- irq isaved is actual return value above | st r0,[r13,160] #arc_pmu.18_27->irq | | bl.d @__request_percpu_irq <-- r0 unchanged so actual irq returned | add r4,r4,r12 #, tmp363, __ptr
Cc: stable@vger.kernel.org Signed-off-by: Vineet Gupta vgupta@synopsys.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arc/kernel/perf_event.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)
--- a/arch/arc/kernel/perf_event.c +++ b/arch/arc/kernel/perf_event.c @@ -562,7 +562,7 @@ static int arc_pmu_device_probe(struct p { struct arc_reg_pct_build pct_bcr; struct arc_reg_cc_build cc_bcr; - int i, has_interrupts, irq; + int i, has_interrupts, irq = -1; int counter_size; /* in bits */
union cc_name { @@ -637,18 +637,27 @@ static int arc_pmu_device_probe(struct p .attr_groups = arc_pmu->attr_groups, };
- if (has_interrupts && (irq = platform_get_irq(pdev, 0) >= 0)) { + if (has_interrupts) { + irq = platform_get_irq(pdev, 0); + if (irq >= 0) { + int ret; + + arc_pmu->irq = irq; + + /* intc map function ensures irq_set_percpu_devid() called */ + ret = request_percpu_irq(irq, arc_pmu_intr, "ARC perf counters", + this_cpu_ptr(&arc_pmu_cpu)); + + if (!ret) + on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1); + else + irq = -1; + }
- arc_pmu->irq = irq; - - /* intc map function ensures irq_set_percpu_devid() called */ - request_percpu_irq(irq, arc_pmu_intr, "ARC perf counters", - this_cpu_ptr(&arc_pmu_cpu)); + }
- on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1); - } else { + if (irq == -1) arc_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT; - }
/* * perf parser doesn't really like '-' symbol in events name, so let's