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87 lines
2.4 KiB
87 lines
2.4 KiB
2 months ago
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From 1a5c0e60308651a20d25ff52511230a20d830330 Mon Sep 17 00:00:00 2001
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From: Logan Gunthorpe <logang@deltatee.com>
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Date: Tue, 4 Jun 2024 10:38:36 -0600
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Subject: [PATCH 102/157] mdadm: Fix hang race condition in
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wait_for_zero_forks()
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Running a create operation with --write-zeros can randomly hang
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forever waiting for child processes. This happens roughly on in
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ten runs with when running with small (20MB) loop devices.
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The bug is caused by the fact that signals can be coallesced into
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one if they are not read by signalfd quick enough. So if two children
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finish at exactly the same time, only one SIGCHLD will be received
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by the parent.
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To fix this, wait on all processes with WNOHANG every time a SIGCHLD
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is received and exit when all processes have been waited on.
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Reported-by: Xiao Ni <xni@redhat.com>
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Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
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Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>
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---
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Create.c | 28 +++++++++++++++-------------
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1 file changed, 15 insertions(+), 13 deletions(-)
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diff --git a/Create.c b/Create.c
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index d033eb68..4f992a22 100644
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--- a/Create.c
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+++ b/Create.c
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@@ -178,6 +178,7 @@ static int wait_for_zero_forks(int *zero_pids, int count)
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bool interrupted = false;
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sigset_t sigset;
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ssize_t s;
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+ pid_t pid;
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for (i = 0; i < count; i++)
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if (zero_pids[i])
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@@ -196,7 +197,7 @@ static int wait_for_zero_forks(int *zero_pids, int count)
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return 1;
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}
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- while (1) {
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+ while (wait_count) {
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s = read(sfd, &fdsi, sizeof(fdsi));
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if (s != sizeof(fdsi)) {
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pr_err("Invalid signalfd read: %s\n", strerror(errno));
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@@ -209,23 +210,24 @@ static int wait_for_zero_forks(int *zero_pids, int count)
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pr_info("Interrupting zeroing processes, please wait...\n");
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interrupted = true;
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} else if (fdsi.ssi_signo == SIGCHLD) {
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- if (!--wait_count)
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- break;
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+ for (i = 0; i < count; i++) {
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+ if (!zero_pids[i])
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+ continue;
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+
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+ pid = waitpid(zero_pids[i], &wstatus, WNOHANG);
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+ if (pid <= 0)
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+ continue;
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+
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+ zero_pids[i] = 0;
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+ if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus))
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+ ret = 1;
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+ wait_count--;
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+ }
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}
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}
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close(sfd);
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- for (i = 0; i < count; i++) {
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- if (!zero_pids[i])
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- continue;
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-
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- waitpid(zero_pids[i], &wstatus, 0);
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- zero_pids[i] = 0;
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- if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus))
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- ret = 1;
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- }
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-
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if (interrupted) {
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pr_err("zeroing interrupted!\n");
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return 1;
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--
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2.41.0
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