Messages in this thread Patch in this message | | | From | (Eric W. Biederman) | Date | Fri, 28 Feb 2020 11:09:19 -0600 | Subject | [PATCH 2/5] posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group |
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As of e78c3496790e ("time, signal: Protect resource use statistics with seqlock") cpu_clock_sample_group no longers needs siglock protection. Unfortunately no one realized it at the time.
Remove the extra locking that is for cpu_clock_sample_group and not for cpu_clock_sample. This significantly simplifies the code.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- kernel/time/posix-cpu-timers.c | 55 +++++----------------------------- 1 file changed, 7 insertions(+), 48 deletions(-)
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 46cc188bf5ab..3b27710f9505 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -721,27 +721,7 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp if (CPUCLOCK_PERTHREAD(timer->it_clock)) { now = cpu_clock_sample(clkid, p); } else { - struct sighand_struct *sighand; - unsigned long flags; - - /* - * Protect against sighand release/switch in exit/exec and - * also make timer sampling safe if it ends up calling - * thread_group_cputime(). - */ - sighand = lock_task_sighand(p, &flags); - if (unlikely(sighand == NULL)) { - /* - * The process has been reaped. - * We can't even collect a sample any more. - * Disarm the timer, nothing else to do. - */ - cpu_timer_setexpires(ctmr, 0); - return; - } else { - now = cpu_clock_sample_group(clkid, p, false); - unlock_task_sighand(p, &flags); - } + now = cpu_clock_sample_group(clkid, p, false); } if (now < expires) { @@ -988,41 +968,20 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) */ if (CPUCLOCK_PERTHREAD(timer->it_clock)) { now = cpu_clock_sample(clkid, p); - bump_cpu_timer(timer, now); - if (unlikely(p->exit_state)) - return; - - /* Protect timer list r/w in arm_timer() */ - sighand = lock_task_sighand(p, &flags); - if (!sighand) - return; } else { - /* - * Protect arm_timer() and timer sampling in case of call to - * thread_group_cputime(). - */ - sighand = lock_task_sighand(p, &flags); - if (unlikely(sighand == NULL)) { - /* - * The process has been reaped. - * We can't even collect a sample any more. - */ - cpu_timer_setexpires(ctmr, 0); - return; - } else if (unlikely(p->exit_state) && thread_group_empty(p)) { - /* If the process is dying, no need to rearm */ - goto unlock; - } now = cpu_clock_sample_group(clkid, p, true); - bump_cpu_timer(timer, now); - /* Leave the sighand locked for the call below. */ } + bump_cpu_timer(timer, now); + + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) + return; /* * Now re-arm for the new expiry time. */ arm_timer(timer); -unlock: unlock_task_sighand(p, &flags); } -- 2.25.0
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