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Wait longer for a previous IPI to be sent

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When sending an IPI, if a previous IPI is still pending delivery,
native_lapic_ipi_vectored() waits for the previous IPI to be sent.
We've seen a few inexplicable panics with the current timeout of 50 ms.
Increase the timeout to 1 second and make it tunable.

No hardware specification mentions a timeout in this case; I checked
the Intel SDM, Intel MP spec, and Intel x2APIC spec.  Linux and illumos
wait forever.  In Linux, see __default_send_IPI_shortcut() in
arch/x86/kernel/apic/ipi.c.  In illumos, see apic_send_ipi() in
usr/src/uts/i86pc/io/pcplusmp/apic_common.c.  However, misbehaving hardware
could hang the system if we wait forever.

Reviewed by:	mav kib
MFC after:	1 week
Sponsored by:	Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D29942
This commit is contained in:
Eric van Gyzen 2021-04-26 10:01:17 -05:00
parent eda28feb2e
commit 2f32a971b7
1 changed files with 7 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
sys/x86/x86/local_apic.c
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@ -202,6 +202,7 @@ static u_long lapic_timer_divisor, count_freq;
static struct eventtimer lapic_et;
#ifdef SMP
static uint64_t lapic_ipi_wait_mult;
static int __read_mostly lapic_ds_idle_timeout = 1000000;
#endif
unsigned int max_apic_id;
@ -212,6 +213,11 @@ SYSCTL_INT(_hw_apic, OID_AUTO, eoi_suppression, CTLFLAG_RD,
&lapic_eoi_suppression, 0, "");
SYSCTL_INT(_hw_apic, OID_AUTO, timer_tsc_deadline, CTLFLAG_RD,
&lapic_timer_tsc_deadline, 0, "");
#ifdef SMP
SYSCTL_INT(_hw_apic, OID_AUTO, ds_idle_timeout, CTLFLAG_RWTUN,
&lapic_ds_idle_timeout, 0,
"timeout (in us) for APIC Delivery Status to become Idle (xAPIC only)");
#endif
static void lapic_calibrate_initcount(struct lapic *la);
static void lapic_calibrate_deadline(struct lapic *la);
@ -2035,7 +2041,6 @@ native_lapic_ipi_raw(register_t icrlo, u_int dest)
}
}
#define BEFORE_SPIN 50000
#ifdef DETECT_DEADLOCK
#define AFTER_SPIN 50
#endif
@ -2082,7 +2087,7 @@ native_lapic_ipi_vectored(u_int vector, int dest)
icrlo |= APIC_DESTMODE_PHY | APIC_TRIGMOD_EDGE | APIC_LEVEL_ASSERT;
/* Wait for an earlier IPI to finish. */
if (!lapic_ipi_wait(BEFORE_SPIN)) {
if (!lapic_ipi_wait(lapic_ds_idle_timeout)) {
if (KERNEL_PANICKED())
return;
else