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Date: Wed, 29 Nov 2017 09:38:48 +0100 From: Jiri Olsa <jolsa@...nel.org> To: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Arnaldo Carvalho de Melo <acme@...nel.org> Cc: lkml <linux-kernel@...r.kernel.org>, Namhyung Kim <namhyung@...nel.org>, David Ahern <dsahern@...il.com>, Andi Kleen <ak@...ux.intel.com>, Milind Chabbi <chabbi.milind@...il.com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Michael Ellerman <mpe@...erman.id.au>, Hari Bathini <hbathini@...ux.vnet.ibm.com>, Jin Yao <yao.jin@...ux.intel.com>, Kan Liang <kan.liang@...el.com>, Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>, Oleg Nesterov <onestero@...hat.com>, Will Deacon <will.deacon@....com> Subject: [PATCH 3/8] hw_breakpoint: Add modify_bp_slot function Adding modify_bp_slot function to keep slot numbers correct when changing the breakpoint type. Using existing __release_bp_slot/__reserve_bp_slot call sequence to update the slot counts. Signed-off-by: Jiri Olsa <jolsa@...nel.org> --- kernel/events/hw_breakpoint.c | 46 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 39 insertions(+), 7 deletions(-) diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index 9b31fbcc3305..776948beb4ac 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -44,6 +44,7 @@ #include <linux/list.h> #include <linux/cpu.h> #include <linux/smp.h> +#include <linux/bug.h> #include <linux/hw_breakpoint.h> /* @@ -344,6 +345,38 @@ void release_bp_slot(struct perf_event *bp) mutex_unlock(&nr_bp_mutex); } +static int __modify_bp_slot(struct perf_event *bp, u64 old_type) +{ + int err; + + __release_bp_slot(bp, old_type); + + err = __reserve_bp_slot(bp, bp->attr.bp_type); + if (err) { + /* + * Reserve the old_type slot back in case + * there's no space for the new type. + * + * This must succeed, because we just released + * the old_type slot in the __release_bp_slot + * call above. If not, something is broken. + */ + WARN_ON(__reserve_bp_slot(bp, old_type)); + } + + return err; +} + +static int modify_bp_slot(struct perf_event *bp, u64 old_type) +{ + int ret; + + mutex_lock(&nr_bp_mutex); + ret = __modify_bp_slot(bp, old_type); + mutex_unlock(&nr_bp_mutex); + return ret; +} + /* * Allow the kernel debugger to reserve breakpoint slots without * taking a lock using the dbg_* variant of for the reserve and @@ -435,6 +468,7 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att u64 old_addr = bp->attr.bp_addr; u64 old_len = bp->attr.bp_len; int old_type = bp->attr.bp_type; + bool modify = attr->bp_type != old_type; int err = 0; /* @@ -452,12 +486,9 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att bp->attr.bp_type = attr->bp_type; bp->attr.bp_len = attr->bp_len; - if (attr->disabled) - goto end; - err = validate_hw_breakpoint(bp); - if (!err) - perf_event_enable(bp); + if (!err && modify) + err = modify_bp_slot(bp, old_type); if (err) { bp->attr.bp_addr = old_addr; @@ -469,9 +500,10 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att return err; } -end: - bp->attr.disabled = attr->disabled; + if (!attr->disabled) + perf_event_enable(bp); + bp->attr.disabled = attr->disabled; return 0; } EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint); -- 2.13.6
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