From ebda41d8de7956f19fd27f86208c668e43c6957c Mon Sep 17 00:00:00 2001 From: Niu Yawei Date: Tue, 3 Nov 2015 01:59:32 -0500 Subject: [PATCH] LU-7330 ldlm: fix race of starting bl threads There is race in the code of starting bl threads which leads to thread number exceeds the maximum number when race happened, it can also lead to duplicated thread name. This patch fixes the race and cleanup the code a bit. Signed-off-by: Niu Yawei Change-Id: I9c9be125d1d76890b8c52476684976dad3cb3d87 Reviewed-on: http://review.whamcloud.com/17026 Tested-by: Jenkins Tested-by: Maloo Reviewed-by: Bobi Jam Reviewed-by: Andreas Dilger --- lustre/ldlm/ldlm_lockd.c | 49 +++++++++++++++++++++++++++--------------------- 1 file changed, 28 insertions(+), 21 deletions(-) diff --git a/lustre/ldlm/ldlm_lockd.c b/lustre/ldlm/ldlm_lockd.c index 651451a..72a6fb2 100644 --- a/lustre/ldlm/ldlm_lockd.c +++ b/lustre/ldlm/ldlm_lockd.c @@ -2600,7 +2600,6 @@ static int ldlm_bl_get_work(struct ldlm_bl_pool *blp, /* This only contains temporary data until the thread starts */ struct ldlm_bl_thread_data { - char bltd_name[CFS_CURPROC_COMM_MAX]; struct ldlm_bl_pool *bltd_blp; struct completion bltd_comp; int bltd_num; @@ -2608,19 +2607,32 @@ struct ldlm_bl_thread_data { static int ldlm_bl_thread_main(void *arg); -static int ldlm_bl_thread_start(struct ldlm_bl_pool *blp) +static int ldlm_bl_thread_start(struct ldlm_bl_pool *blp, bool check_busy) { struct ldlm_bl_thread_data bltd = { .bltd_blp = blp }; struct task_struct *task; init_completion(&bltd.bltd_comp); - bltd.bltd_num = atomic_read(&blp->blp_num_threads); - snprintf(bltd.bltd_name, sizeof(bltd.bltd_name) - 1, - "ldlm_bl_%02d", bltd.bltd_num); - task = kthread_run(ldlm_bl_thread_main, &bltd, bltd.bltd_name); + + bltd.bltd_num = atomic_inc_return(&blp->blp_num_threads); + if (bltd.bltd_num >= blp->blp_max_threads) { + atomic_dec(&blp->blp_num_threads); + return 0; + } + + LASSERTF(bltd.bltd_num > 0, "thread num:%d\n", bltd.bltd_num); + if (check_busy && + atomic_read(&blp->blp_busy_threads) < (bltd.bltd_num - 1)) { + atomic_dec(&blp->blp_num_threads); + return 0; + } + + task = kthread_run(ldlm_bl_thread_main, &bltd, "ldlm_bl_%02d", + bltd.bltd_num); if (IS_ERR(task)) { CERROR("cannot start LDLM thread ldlm_bl_%02d: rc %ld\n", - atomic_read(&blp->blp_num_threads), PTR_ERR(task)); + bltd.bltd_num, PTR_ERR(task)); + atomic_dec(&blp->blp_num_threads); return PTR_ERR(task); } wait_for_completion(&bltd.bltd_comp); @@ -2632,12 +2644,11 @@ static int ldlm_bl_thread_start(struct ldlm_bl_pool *blp) static int ldlm_bl_thread_need_create(struct ldlm_bl_pool *blp, struct ldlm_bl_work_item *blwi) { - int busy = atomic_read(&blp->blp_busy_threads); - - if (busy >= blp->blp_max_threads) + if (atomic_read(&blp->blp_num_threads) >= blp->blp_max_threads) return 0; - if (busy < atomic_read(&blp->blp_num_threads)) + if (atomic_read(&blp->blp_busy_threads) < + atomic_read(&blp->blp_num_threads)) return 0; if (blwi != NULL && (blwi->blwi_ns == NULL || @@ -2726,9 +2737,6 @@ static int ldlm_bl_thread_main(void *arg) blp = bltd->bltd_blp; - atomic_inc(&blp->blp_num_threads); - atomic_inc(&blp->blp_busy_threads); - complete(&bltd->bltd_comp); /* cannot use bltd after this, it is only on caller's stack */ @@ -2740,29 +2748,28 @@ static int ldlm_bl_thread_main(void *arg) rc = ldlm_bl_get_work(blp, &blwi, &exp); - if (rc == 0) { - atomic_dec(&blp->blp_busy_threads); + if (rc == 0) l_wait_event_exclusive(blp->blp_waitq, ldlm_bl_get_work(blp, &blwi, &exp), &lwi); - atomic_inc(&blp->blp_busy_threads); - } + atomic_inc(&blp->blp_busy_threads); if (ldlm_bl_thread_need_create(blp, blwi)) /* discard the return value, we tried */ - ldlm_bl_thread_start(blp); + ldlm_bl_thread_start(blp, true); if (exp) rc = ldlm_bl_thread_exports(blp, exp); else if (blwi) rc = ldlm_bl_thread_blwi(blp, blwi); + atomic_dec(&blp->blp_busy_threads); + if (rc == LDLM_ITER_STOP) break; } - atomic_dec(&blp->blp_busy_threads); atomic_dec(&blp->blp_num_threads); complete(&blp->blp_comp); RETURN(0); @@ -3042,7 +3049,7 @@ static int ldlm_setup(void) } for (i = 0; i < blp->blp_min_threads; i++) { - rc = ldlm_bl_thread_start(blp); + rc = ldlm_bl_thread_start(blp, false); if (rc < 0) GOTO(out, rc); } -- 1.8.3.1