| Message ID | 1414606478-13709-2-git-send-email-sboyd@codeaurora.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
On 29/10/14 18:14, Stephen Boyd wrote: > The handle_rx() path calls uart_handle_sysrq_char() with the port > lock held. This causes a spinlock recursion. Release and > reacquire the lock here to avoid this. > > BUG: spinlock recursion on CPU#0, swapper/0 > lock: msm_uart_ports+0x1e0/0x2d0, .magic: dead4ead, .owner: swapper/0, .owner_cpu: 0 > CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-rc7-00012-gb38ee8265941 #69 > [<c0013964>] (unwind_backtrace) from [<c0011f74>] (show_stack+0x10/0x14) > [<c0011f74>] (show_stack) from [<c004ed1c>] (do_raw_spin_lock+0x11c/0x13c) > [<c004ed1c>] (do_raw_spin_lock) from [<c02d44c0>] (msm_console_write+0x78/0x188) > [<c02d44c0>] (msm_console_write) from [<c0052880>] (call_console_drivers.constprop.22+0xb4/0x144) > [<c0052880>] (call_console_drivers.constprop.22) from [<c0053570>] (console_unlock+0x27c/0x4ac) > [<c0053570>] (console_unlock) from [<c0053bb4>] (vprintk_emit+0x1f4/0x5a8) > [<c0053bb4>] (vprintk_emit) from [<c04ad0ac>] (printk+0x30/0x40) > [<c04ad0ac>] (printk) from [<c02c2990>] (__handle_sysrq+0x58/0x1b8) > [<c02c2990>] (__handle_sysrq) from [<c02d41b0>] (msm_irq+0x694/0x6f8) > [<c02d41b0>] (msm_irq) from [<c0055740>] (handle_irq_event_percpu+0x58/0x270) > [<c0055740>] (handle_irq_event_percpu) from [<c0055994>] (handle_irq_event+0x3c/0x5c) > [<c0055994>] (handle_irq_event) from [<c0057e84>] (handle_level_irq+0x9c/0x138) > [<c0057e84>] (handle_level_irq) from [<c005509c>] (generic_handle_irq+0x24/0x38) > [<c005509c>] (generic_handle_irq) from [<c000f730>] (handle_IRQ+0x44/0xb0) > [<c000f730>] (handle_IRQ) from [<c0008518>] (msm_vic_handle_irq+0x44/0x64) > [<c0008518>] (msm_vic_handle_irq) from [<c04b5ac4>] (__irq_svc+0x44/0x7c) > Exception stack(0xc0719f68 to 0xc0719fb0) > 9f60: 00000001 00000001 00000000 c0722938 c0718000 c0769acc > 9f80: 00000000 c0720098 c0769305 4117b362 c0769acc 00000000 01000000 c0719fb0 > 9fa0: c004cab0 c000f880 20000013 ffffffff > [<c04b5ac4>] (__irq_svc) from [<c000f880>] (arch_cpu_idle+0x20/0x30) > [<c000f880>] (arch_cpu_idle) from [<c004691c>] (cpu_startup_entry+0xf4/0x23c) > [<c004691c>] (cpu_startup_entry) from [<c06d8b70>] (start_kernel+0x32c/0x394) > > Cc: Frank Rowand <frank.rowand@sonymobile.com> > Cc: Daniel Thompson <daniel.thompson@linaro.org> > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> > --- > drivers/tty/serial/msm_serial.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c > index 4b6c78331a64..cedcc36762a2 100644 > --- a/drivers/tty/serial/msm_serial.c > +++ b/drivers/tty/serial/msm_serial.c > @@ -174,6 +174,7 @@ static void handle_rx(struct uart_port *port) > while ((sr = msm_read(port, UART_SR)) & UART_SR_RX_READY) { > unsigned int c; > char flag = TTY_NORMAL; > + int sysrq; > > c = msm_read(port, UART_RF); > > @@ -195,7 +196,10 @@ static void handle_rx(struct uart_port *port) > else if (sr & UART_SR_PAR_FRAME_ERR) > flag = TTY_FRAME; > > - if (!uart_handle_sysrq_char(port, c)) > + spin_unlock(&port->lock); > + sysrq = uart_handle_sysrq_char(port, c); > + spin_lock(&port->lock); > + if (!sysrq) > tty_insert_flip_char(tport, c, flag); Does tty_insert_flip_char() need the port to be locked? -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/30/2014 07:26 AM, Daniel Thompson wrote: > On 29/10/14 18:14, Stephen Boyd wrote: >> The handle_rx() path calls uart_handle_sysrq_char() with the port >> lock held. This causes a spinlock recursion. Release and >> reacquire the lock here to avoid this. >> >> BUG: spinlock recursion on CPU#0, swapper/0 >> lock: msm_uart_ports+0x1e0/0x2d0, .magic: dead4ead, .owner: swapper/0, .owner_cpu: 0 >> CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-rc7-00012-gb38ee8265941 #69 >> [<c0013964>] (unwind_backtrace) from [<c0011f74>] (show_stack+0x10/0x14) >> [<c0011f74>] (show_stack) from [<c004ed1c>] (do_raw_spin_lock+0x11c/0x13c) >> [<c004ed1c>] (do_raw_spin_lock) from [<c02d44c0>] (msm_console_write+0x78/0x188) >> [<c02d44c0>] (msm_console_write) from [<c0052880>] (call_console_drivers.constprop.22+0xb4/0x144) >> [<c0052880>] (call_console_drivers.constprop.22) from [<c0053570>] (console_unlock+0x27c/0x4ac) >> [<c0053570>] (console_unlock) from [<c0053bb4>] (vprintk_emit+0x1f4/0x5a8) >> [<c0053bb4>] (vprintk_emit) from [<c04ad0ac>] (printk+0x30/0x40) >> [<c04ad0ac>] (printk) from [<c02c2990>] (__handle_sysrq+0x58/0x1b8) >> [<c02c2990>] (__handle_sysrq) from [<c02d41b0>] (msm_irq+0x694/0x6f8) >> [<c02d41b0>] (msm_irq) from [<c0055740>] (handle_irq_event_percpu+0x58/0x270) >> [<c0055740>] (handle_irq_event_percpu) from [<c0055994>] (handle_irq_event+0x3c/0x5c) >> [<c0055994>] (handle_irq_event) from [<c0057e84>] (handle_level_irq+0x9c/0x138) >> [<c0057e84>] (handle_level_irq) from [<c005509c>] (generic_handle_irq+0x24/0x38) >> [<c005509c>] (generic_handle_irq) from [<c000f730>] (handle_IRQ+0x44/0xb0) >> [<c000f730>] (handle_IRQ) from [<c0008518>] (msm_vic_handle_irq+0x44/0x64) >> [<c0008518>] (msm_vic_handle_irq) from [<c04b5ac4>] (__irq_svc+0x44/0x7c) >> Exception stack(0xc0719f68 to 0xc0719fb0) >> 9f60: 00000001 00000001 00000000 c0722938 c0718000 c0769acc >> 9f80: 00000000 c0720098 c0769305 4117b362 c0769acc 00000000 01000000 c0719fb0 >> 9fa0: c004cab0 c000f880 20000013 ffffffff >> [<c04b5ac4>] (__irq_svc) from [<c000f880>] (arch_cpu_idle+0x20/0x30) >> [<c000f880>] (arch_cpu_idle) from [<c004691c>] (cpu_startup_entry+0xf4/0x23c) >> [<c004691c>] (cpu_startup_entry) from [<c06d8b70>] (start_kernel+0x32c/0x394) >> >> Cc: Frank Rowand <frank.rowand@sonymobile.com> >> Cc: Daniel Thompson <daniel.thompson@linaro.org> >> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> >> --- >> drivers/tty/serial/msm_serial.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c >> index 4b6c78331a64..cedcc36762a2 100644 >> --- a/drivers/tty/serial/msm_serial.c >> +++ b/drivers/tty/serial/msm_serial.c >> @@ -174,6 +174,7 @@ static void handle_rx(struct uart_port *port) >> while ((sr = msm_read(port, UART_SR)) & UART_SR_RX_READY) { >> unsigned int c; >> char flag = TTY_NORMAL; >> + int sysrq; >> >> c = msm_read(port, UART_RF); >> >> @@ -195,7 +196,10 @@ static void handle_rx(struct uart_port *port) >> else if (sr & UART_SR_PAR_FRAME_ERR) >> flag = TTY_FRAME; >> >> - if (!uart_handle_sysrq_char(port, c)) >> + spin_unlock(&port->lock); >> + sysrq = uart_handle_sysrq_char(port, c); >> + spin_lock(&port->lock); >> + if (!sysrq) >> tty_insert_flip_char(tport, c, flag); > > Does tty_insert_flip_char() need the port to be locked? No. It does not serialize internally, so concurrent use will blow up, but that doesn't look possible here. Can bad things happen if a well-timed set_termios() happens while the lock is dropped? Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 4b6c78331a64..cedcc36762a2 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -174,6 +174,7 @@ static void handle_rx(struct uart_port *port) while ((sr = msm_read(port, UART_SR)) & UART_SR_RX_READY) { unsigned int c; char flag = TTY_NORMAL; + int sysrq; c = msm_read(port, UART_RF); @@ -195,7 +196,10 @@ static void handle_rx(struct uart_port *port) else if (sr & UART_SR_PAR_FRAME_ERR) flag = TTY_FRAME; - if (!uart_handle_sysrq_char(port, c)) + spin_unlock(&port->lock); + sysrq = uart_handle_sysrq_char(port, c); + spin_lock(&port->lock); + if (!sysrq) tty_insert_flip_char(tport, c, flag); }
The handle_rx() path calls uart_handle_sysrq_char() with the port lock held. This causes a spinlock recursion. Release and reacquire the lock here to avoid this. BUG: spinlock recursion on CPU#0, swapper/0 lock: msm_uart_ports+0x1e0/0x2d0, .magic: dead4ead, .owner: swapper/0, .owner_cpu: 0 CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-rc7-00012-gb38ee8265941 #69 [<c0013964>] (unwind_backtrace) from [<c0011f74>] (show_stack+0x10/0x14) [<c0011f74>] (show_stack) from [<c004ed1c>] (do_raw_spin_lock+0x11c/0x13c) [<c004ed1c>] (do_raw_spin_lock) from [<c02d44c0>] (msm_console_write+0x78/0x188) [<c02d44c0>] (msm_console_write) from [<c0052880>] (call_console_drivers.constprop.22+0xb4/0x144) [<c0052880>] (call_console_drivers.constprop.22) from [<c0053570>] (console_unlock+0x27c/0x4ac) [<c0053570>] (console_unlock) from [<c0053bb4>] (vprintk_emit+0x1f4/0x5a8) [<c0053bb4>] (vprintk_emit) from [<c04ad0ac>] (printk+0x30/0x40) [<c04ad0ac>] (printk) from [<c02c2990>] (__handle_sysrq+0x58/0x1b8) [<c02c2990>] (__handle_sysrq) from [<c02d41b0>] (msm_irq+0x694/0x6f8) [<c02d41b0>] (msm_irq) from [<c0055740>] (handle_irq_event_percpu+0x58/0x270) [<c0055740>] (handle_irq_event_percpu) from [<c0055994>] (handle_irq_event+0x3c/0x5c) [<c0055994>] (handle_irq_event) from [<c0057e84>] (handle_level_irq+0x9c/0x138) [<c0057e84>] (handle_level_irq) from [<c005509c>] (generic_handle_irq+0x24/0x38) [<c005509c>] (generic_handle_irq) from [<c000f730>] (handle_IRQ+0x44/0xb0) [<c000f730>] (handle_IRQ) from [<c0008518>] (msm_vic_handle_irq+0x44/0x64) [<c0008518>] (msm_vic_handle_irq) from [<c04b5ac4>] (__irq_svc+0x44/0x7c) Exception stack(0xc0719f68 to 0xc0719fb0) 9f60: 00000001 00000001 00000000 c0722938 c0718000 c0769acc 9f80: 00000000 c0720098 c0769305 4117b362 c0769acc 00000000 01000000 c0719fb0 9fa0: c004cab0 c000f880 20000013 ffffffff [<c04b5ac4>] (__irq_svc) from [<c000f880>] (arch_cpu_idle+0x20/0x30) [<c000f880>] (arch_cpu_idle) from [<c004691c>] (cpu_startup_entry+0xf4/0x23c) [<c004691c>] (cpu_startup_entry) from [<c06d8b70>] (start_kernel+0x32c/0x394) Cc: Frank Rowand <frank.rowand@sonymobile.com> Cc: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- drivers/tty/serial/msm_serial.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)