From 79337212b5ee0c8c4a3170fb2ed01ccd59830f0b Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Thu, 22 Oct 2020 03:16:22 -0700 Subject: [PATCH] ARC: perf: redo the pct irq missing in device-tree handling 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: Signed-off-by: Vineet Gupta Signed-off-by: Greg Kroah-Hartman --- arch/arc/kernel/perf_event.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/arch/arc/kernel/perf_event.c b/arch/arc/kernel/perf_event.c index 79849f37e782c..145722f80c9b7 100644 --- 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 platform_device *pdev) { 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 { @@ -637,19 +637,28 @@ static int arc_pmu_device_probe(struct platform_device *pdev) .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; + 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)); + /* 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; + } - on_each_cpu(arc_cpu_pmu_irq_init, &irq, 1); - } else { - arc_pmu->pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT; } + 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 * use '_' in arc pct name as it goes to kernel PMU event prefix.